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	$104.86	6.310%	$111.4767	$111.48	$111.50	$111.50
Purchase #2	$70.97	12.807%	$80.0591	$80.06	$80.05	$80.10
Purchase #3	$144.75	5.207%	$152.2871	$152.29	$152.30	$152.30
Purchase #4	$223.83	8.266%	$242.3318	$242.33	$242.35	$242.30
Purchase #5	$59.32	5.376%	$62.509	$62.51	$62.50	$62.50
Purchase #6	$8.74	7.560%	$9.4007	$9.40	$9.40	$9.40
Purchase #7	$39.65	12.106%	$44.45	$44.45	$44.45	$44.50
7 purchase totals =	$652.12		$702.5144	$702.52	$702.55	$702.60