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	$101.82	4.651%	$106.5556	$106.56	$106.55	$106.60
Purchase #2	$229.89	4.702%	$240.6994	$240.70	$240.70	$240.70
Purchase #3	$81.60	8.706%	$88.7041	$88.70	$88.70	$88.70
Purchase #4	$70.30	12.272%	$78.9272	$78.93	$78.95	$78.90
Purchase #5	$81.45	3.267%	$84.111	$84.11	$84.10	$84.10
Purchase #6	$93.72	6.515%	$99.8259	$99.83	$99.85	$99.80
Purchase #7	$141.38	13.706%	$160.7575	$160.76	$160.75	$160.80
7 purchase totals =	$800.16		$859.5807	$859.59	$859.60	$859.60