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	$94.55	4.600%	$98.8993	$98.90	$98.90	$98.90
Purchase #2	$147.44	13.573%	$167.452	$167.45	$167.45	$167.50
Purchase #3	$206.38	7.145%	$221.1259	$221.13	$221.15	$221.10
Purchase #4	$229.60	12.125%	$257.439	$257.44	$257.45	$257.40
Purchase #5	$196.29	13.183%	$222.1669	$222.17	$222.15	$222.20
Purchase #6	$45.73	10.678%	$50.613	$50.61	$50.60	$50.60
Purchase #7	$203.33	3.230%	$209.8976	$209.90	$209.90	$209.90
7 purchase totals =	$1,123.32		$1,227.5937	$1,227.60	$1,227.60	$1,227.60