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	$199.78	11.153%	$222.0615	$222.06	$222.05	$222.10
Purchase #2	$105.25	5.610%	$111.1545	$111.15	$111.15	$111.20
Purchase #3	$44.50	12.351%	$49.9962	$50.00	$50.00	$50.00
Purchase #4	$137.34	3.305%	$141.8791	$141.88	$141.90	$141.90
Purchase #5	$151.34	3.639%	$156.8473	$156.85	$156.85	$156.80
Purchase #6	$236.96	5.549%	$250.1089	$250.11	$250.10	$250.10
Purchase #7	$214.62	6.749%	$229.1047	$229.10	$229.10	$229.10
7 purchase totals =	$1,089.79		$1,161.1522	$1,161.15	$1,161.15	$1,161.20