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	$197.39	7.741%	$212.67	$212.67	$212.65	$212.70
Purchase #2	$105.66	5.821%	$111.8105	$111.81	$111.80	$111.80
Purchase #3	$113.52	4.257%	$118.3525	$118.35	$118.35	$118.40
Purchase #4	$99.37	10.125%	$109.4312	$109.43	$109.45	$109.40
Purchase #5	$167.42	9.156%	$182.749	$182.75	$182.75	$182.70
Purchase #6	$67.67	8.419%	$73.3671	$73.37	$73.35	$73.40
Purchase #7	$111.95	10.153%	$123.3163	$123.32	$123.30	$123.30
7 purchase totals =	$862.98		$931.6966	$931.70	$931.65	$931.70