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	$201.64	13.528%	$228.9179	$228.92	$228.90	$228.90
Purchase #2	$105.72	13.651%	$120.1518	$120.15	$120.15	$120.20
Purchase #3	$57.67	6.742%	$61.5581	$61.56	$61.55	$61.60
Purchase #4	$52.36	10.501%	$57.8583	$57.86	$57.85	$57.90
Purchase #5	$141.36	6.871%	$151.0728	$151.07	$151.05	$151.10
Purchase #6	$221.72	10.654%	$245.342	$245.34	$245.35	$245.30
Purchase #7	$80.32	11.626%	$89.658	$89.66	$89.65	$89.70
7 purchase totals =	$860.79		$954.5589	$954.56	$954.50	$954.70