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	$198.47	6.172%	$210.7196	$210.72	$210.70	$210.70
Purchase #2	$190.64	4.458%	$199.1387	$199.14	$199.15	$199.10
Purchase #3	$32.77	7.278%	$35.155	$35.16	$35.15	$35.20
Purchase #4	$221.54	3.620%	$229.5597	$229.56	$229.55	$229.60
Purchase #5	$128.56	10.652%	$142.2542	$142.25	$142.25	$142.30
Purchase #6	$22.57	9.777%	$24.7767	$24.78	$24.80	$24.80
Purchase #7	$214.37	4.245%	$223.47	$223.47	$223.45	$223.50
7 purchase totals =	$1,008.92		$1,065.0739	$1,065.08	$1,065.05	$1,065.20