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	$115.85	13.214%	$131.1584	$131.16	$131.15	$131.20
Purchase #2	$158.45	8.505%	$171.9262	$171.93	$171.95	$171.90
Purchase #3	$55.30	9.823%	$60.7321	$60.73	$60.75	$60.70
Purchase #4	$93.35	7.364%	$100.2243	$100.22	$100.20	$100.20
Purchase #5	$87.60	4.391%	$91.4465	$91.45	$91.45	$91.40
Purchase #6	$170.67	10.680%	$188.8976	$188.90	$188.90	$188.90
Purchase #7	$242.66	11.303%	$270.0879	$270.09	$270.10	$270.10
7 purchase totals =	$923.88		$1,014.4730	$1,014.48	$1,014.50	$1,014.40