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	$47.68	9.664%	$52.2878	$52.29	$52.30	$52.30
Purchase #2	$88.90	5.732%	$93.9957	$94.00	$94.00	$94.00
Purchase #3	$227.69	13.343%	$258.0707	$258.07	$258.05	$258.10
Purchase #4	$84.88	5.672%	$89.6944	$89.69	$89.70	$89.70
Purchase #5	$161.59	6.368%	$171.8801	$171.88	$171.90	$171.90
Purchase #6	$29.56	10.485%	$32.6594	$32.66	$32.65	$32.70
Purchase #7	$160.32	3.454%	$165.8575	$165.86	$165.85	$165.90
7 purchase totals =	$800.62		$864.4456	$864.45	$864.45	$864.60