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	$101.34	5.410%	$106.8225	$106.82	$106.80	$106.80
Purchase #2	$139.53	3.746%	$144.7568	$144.76	$144.75	$144.80
Purchase #3	$165.73	13.520%	$188.1367	$188.14	$188.15	$188.10
Purchase #4	$18.78	4.551%	$19.6347	$19.63	$19.65	$19.60
Purchase #5	$119.30	6.556%	$127.1213	$127.12	$127.10	$127.10
Purchase #6	$210.89	6.540%	$224.6822	$224.68	$224.70	$224.70
Purchase #7	$196.31	13.777%	$223.3556	$223.36	$223.35	$223.40
7 purchase totals =	$951.88		$1,034.5098	$1,034.51	$1,034.50	$1,034.50