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	$157.53	11.532%	$175.6964	$175.70	$175.70	$175.70
Purchase #2	$97.38	8.495%	$105.6524	$105.65	$105.65	$105.70
Purchase #3	$26.59	3.274%	$27.4606	$27.46	$27.45	$27.50
Purchase #4	$239.92	5.655%	$253.4875	$253.49	$253.50	$253.50
Purchase #5	$79.27	4.605%	$82.9204	$82.92	$82.90	$82.90
Purchase #6	$171.80	11.592%	$191.7151	$191.72	$191.70	$191.70
Purchase #7	$82.54	8.367%	$89.4461	$89.45	$89.45	$89.40
7 purchase totals =	$855.03		$926.3785	$926.39	$926.35	$926.40