Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$243.40	10.648%	$269.3172	$269.32	$269.30	$269.30
Purchase #2	$191.31	11.374%	$213.0696	$213.07	$213.05	$213.10
Purchase #3	$177.39	10.160%	$195.4128	$195.41	$195.40	$195.40
Purchase #4	$240.78	10.725%	$266.6037	$266.60	$266.60	$266.60
Purchase #5	$174.45	9.765%	$191.485	$191.49	$191.50	$191.50
Purchase #6	$114.77	11.434%	$127.8928	$127.89	$127.90	$127.90
Purchase #7	$174.84	12.447%	$196.6023	$196.60	$196.60	$196.60
7 purchase totals =	$1,316.94		$1,460.3834	$1,460.38	$1,460.35	$1,460.40