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	$242.54	3.343%	$250.6481	$250.65	$250.65	$250.60
Purchase #2	$81.48	4.510%	$85.1547	$85.15	$85.15	$85.20
Purchase #3	$120.56	5.466%	$127.1498	$127.15	$127.15	$127.10
Purchase #4	$243.51	13.185%	$275.6168	$275.62	$275.60	$275.60
Purchase #5	$47.82	6.429%	$50.8943	$50.89	$50.90	$50.90
Purchase #6	$180.83	5.523%	$190.8172	$190.82	$190.80	$190.80
Purchase #7	$179.55	13.539%	$203.8593	$203.86	$203.85	$203.90
7 purchase totals =	$1,096.29		$1,184.1402	$1,184.14	$1,184.10	$1,184.10