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	$41.81	3.199%	$43.1475	$43.15	$43.15	$43.10
Purchase #2	$165.93	13.494%	$188.3206	$188.32	$188.30	$188.30
Purchase #3	$127.99	3.792%	$132.8434	$132.84	$132.85	$132.80
Purchase #4	$153.33	4.668%	$160.4874	$160.49	$160.50	$160.50
Purchase #5	$13.86	5.743%	$14.656	$14.66	$14.65	$14.70
Purchase #6	$227.83	12.238%	$255.7118	$255.71	$255.70	$255.70
Purchase #7	$231.33	5.166%	$243.2805	$243.28	$243.30	$243.30
7 purchase totals =	$962.08		$1,038.4472	$1,038.45	$1,038.45	$1,038.40