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	$210.28	7.312%	$225.6557	$225.66	$225.65	$225.70
Purchase #2	$123.61	3.745%	$128.2392	$128.24	$128.25	$128.20
Purchase #3	$40.55	13.335%	$45.9573	$45.96	$45.95	$46.00
Purchase #4	$217.80	13.318%	$246.8066	$246.81	$246.80	$246.80
Purchase #5	$140.33	7.620%	$151.0231	$151.02	$151.00	$151.00
Purchase #6	$213.35	4.720%	$223.4201	$223.42	$223.40	$223.40
Purchase #7	$25.65	10.364%	$28.3084	$28.31	$28.30	$28.30
7 purchase totals =	$971.57		$1,049.4104	$1,049.42	$1,049.35	$1,049.40