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	$234.69	13.300%	$265.9038	$265.90	$265.90	$265.90
Purchase #2	$18.76	3.587%	$19.4329	$19.43	$19.45	$19.40
Purchase #3	$128.79	11.186%	$143.1964	$143.20	$143.20	$143.20
Purchase #4	$131.54	7.428%	$141.3108	$141.31	$141.30	$141.30
Purchase #5	$226.58	7.406%	$243.3605	$243.36	$243.35	$243.40
Purchase #6	$55.61	10.786%	$61.6081	$61.61	$61.60	$61.60
Purchase #7	$130.91	8.405%	$141.913	$141.91	$141.90	$141.90
7 purchase totals =	$926.88		$1,016.7255	$1,016.72	$1,016.70	$1,016.70