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	$219.37	12.392%	$246.5543	$246.55	$246.55	$246.60
Purchase #2	$103.85	7.155%	$111.2805	$111.28	$111.30	$111.30
Purchase #3	$30.73	9.747%	$33.7253	$33.73	$33.75	$33.70
Purchase #4	$168.64	13.403%	$191.2428	$191.24	$191.25	$191.20
Purchase #5	$60.33	9.584%	$66.112	$66.11	$66.10	$66.10
Purchase #6	$209.89	4.774%	$219.9101	$219.91	$219.90	$219.90
Purchase #7	$164.35	7.589%	$176.8225	$176.82	$176.80	$176.80
7 purchase totals =	$957.16		$1,045.6475	$1,045.64	$1,045.65	$1,045.60