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	$182.74	3.301%	$188.7722	$188.77	$188.75	$188.80
Purchase #2	$159.60	7.840%	$172.1126	$172.11	$172.10	$172.10
Purchase #3	$84.48	10.657%	$93.483	$93.48	$93.50	$93.50
Purchase #4	$73.92	6.152%	$78.4676	$78.47	$78.45	$78.50
Purchase #5	$146.58	8.733%	$159.3808	$159.38	$159.40	$159.40
Purchase #6	$199.48	5.305%	$210.0624	$210.06	$210.05	$210.10
Purchase #7	$103.38	7.203%	$110.8265	$110.83	$110.85	$110.80
7 purchase totals =	$950.18		$1,013.1051	$1,013.10	$1,013.10	$1,013.20