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	$119.89	11.244%	$133.3704	$133.37	$133.35	$133.40
Purchase #2	$73.52	6.659%	$78.4157	$78.42	$78.40	$78.40
Purchase #3	$179.63	6.792%	$191.8305	$191.83	$191.85	$191.80
Purchase #4	$123.49	12.831%	$139.335	$139.34	$139.35	$139.30
Purchase #5	$95.39	11.511%	$106.3703	$106.37	$106.35	$106.40
Purchase #6	$154.91	7.106%	$165.9179	$165.92	$165.90	$165.90
Purchase #7	$122.84	13.199%	$139.0537	$139.05	$139.05	$139.10
7 purchase totals =	$869.67		$954.2935	$954.30	$954.25	$954.30