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	$139.49	7.874%	$150.4734	$150.47	$150.45	$150.50
Purchase #2	$59.31	9.183%	$64.7564	$64.76	$64.75	$64.80
Purchase #3	$178.40	8.111%	$192.87	$192.87	$192.85	$192.90
Purchase #4	$211.37	11.425%	$235.519	$235.52	$235.50	$235.50
Purchase #5	$55.89	12.172%	$62.6929	$62.69	$62.70	$62.70
Purchase #6	$84.45	9.405%	$92.3925	$92.39	$92.40	$92.40
Purchase #7	$245.88	8.418%	$266.5782	$266.58	$266.60	$266.60
7 purchase totals =	$974.79		$1,065.2824	$1,065.28	$1,065.25	$1,065.40