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	$107.29	4.179%	$111.7736	$111.77	$111.75	$111.80
Purchase #2	$84.94	10.332%	$93.716	$93.72	$93.70	$93.70
Purchase #3	$78.96	6.208%	$83.8618	$83.86	$83.85	$83.90
Purchase #4	$195.83	13.228%	$221.7344	$221.73	$221.75	$221.70
Purchase #5	$86.58	5.851%	$91.6458	$91.65	$91.65	$91.60
Purchase #6	$66.71	5.355%	$70.2823	$70.28	$70.30	$70.30
Purchase #7	$30.62	10.485%	$33.8305	$33.83	$33.85	$33.80
7 purchase totals =	$650.93		$706.8444	$706.84	$706.85	$706.80