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	$73.45	12.403%	$82.56	$82.56	$82.55	$82.60
Purchase #2	$143.45	8.469%	$155.5988	$155.60	$155.60	$155.60
Purchase #3	$188.33	4.661%	$197.1081	$197.11	$197.10	$197.10
Purchase #4	$9.75	11.702%	$10.8909	$10.89	$10.90	$10.90
Purchase #5	$199.88	12.850%	$225.5646	$225.56	$225.55	$225.60
Purchase #6	$249.39	10.134%	$274.6632	$274.66	$274.65	$274.70
Purchase #7	$100.41	11.326%	$111.7824	$111.78	$111.80	$111.80
7 purchase totals =	$964.66		$1,058.1680	$1,058.16	$1,058.15	$1,058.30