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	$172.47	9.424%	$188.7236	$188.72	$188.70	$188.70
Purchase #2	$236.83	11.164%	$263.2697	$263.27	$263.25	$263.30
Purchase #3	$187.25	3.673%	$194.1277	$194.13	$194.15	$194.10
Purchase #4	$69.76	4.433%	$72.8525	$72.85	$72.85	$72.90
Purchase #5	$91.95	3.642%	$95.2988	$95.30	$95.30	$95.30
Purchase #6	$155.93	6.388%	$165.8908	$165.89	$165.90	$165.90
Purchase #7	$240.51	5.541%	$253.8367	$253.84	$253.85	$253.80
7 purchase totals =	$1,154.70		$1,233.9998	$1,234.00	$1,234.00	$1,234.00