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	$147.87	4.680%	$154.7903	$154.79	$154.80	$154.80
Purchase #2	$218.49	13.622%	$248.2527	$248.25	$248.25	$248.30
Purchase #3	$59.49	10.157%	$65.5324	$65.53	$65.55	$65.50
Purchase #4	$182.97	7.386%	$196.4842	$196.48	$196.50	$196.50
Purchase #5	$129.91	10.496%	$143.5454	$143.55	$143.55	$143.50
Purchase #6	$76.28	9.286%	$83.3634	$83.36	$83.35	$83.40
Purchase #7	$131.46	11.699%	$146.8395	$146.84	$146.85	$146.80
7 purchase totals =	$946.47		$1,038.8079	$1,038.80	$1,038.85	$1,038.80