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	$67.35	4.446%	$70.3444	$70.34	$70.35	$70.30
Purchase #2	$124.77	3.148%	$128.6978	$128.70	$128.70	$128.70
Purchase #3	$84.56	5.750%	$89.4222	$89.42	$89.40	$89.40
Purchase #4	$233.78	10.588%	$258.5326	$258.53	$258.55	$258.50
Purchase #5	$190.63	12.426%	$214.3177	$214.32	$214.30	$214.30
Purchase #6	$55.28	5.418%	$58.2751	$58.28	$58.30	$58.30
Purchase #7	$78.34	4.774%	$82.08	$82.08	$82.10	$82.10
7 purchase totals =	$834.71		$901.6698	$901.67	$901.70	$901.60