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	$58.28	3.663%	$60.4148	$60.41	$60.40	$60.40
Purchase #2	$47.78	9.195%	$52.1734	$52.17	$52.15	$52.20
Purchase #3	$58.32	12.568%	$65.6497	$65.65	$65.65	$65.60
Purchase #4	$66.29	9.361%	$72.4954	$72.50	$72.50	$72.50
Purchase #5	$81.26	5.444%	$85.6838	$85.68	$85.70	$85.70
Purchase #6	$72.50	13.580%	$82.3455	$82.35	$82.35	$82.30
Purchase #7	$108.32	3.220%	$111.8079	$111.81	$111.80	$111.80
7 purchase totals =	$492.75		$530.5705	$530.57	$530.55	$530.50