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	$82.48	5.110%	$86.6947	$86.69	$86.70	$86.70
Purchase #2	$88.60	10.355%	$97.7745	$97.77	$97.75	$97.80
Purchase #3	$169.40	3.682%	$175.6373	$175.64	$175.65	$175.60
Purchase #4	$112.89	12.758%	$127.2925	$127.29	$127.30	$127.30
Purchase #5	$220.72	11.656%	$246.4471	$246.45	$246.45	$246.40
Purchase #6	$176.79	12.231%	$198.4132	$198.41	$198.40	$198.40
Purchase #7	$179.72	6.536%	$191.4665	$191.47	$191.45	$191.50
7 purchase totals =	$1,030.60		$1,123.7258	$1,123.72	$1,123.70	$1,123.70