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	$212.67	11.419%	$236.9548	$236.95	$236.95	$237.00
Purchase #2	$61.54	13.572%	$69.8922	$69.89	$69.90	$69.90
Purchase #3	$221.31	9.860%	$243.1312	$243.13	$243.15	$243.10
Purchase #4	$127.76	13.855%	$145.4611	$145.46	$145.45	$145.50
Purchase #5	$57.63	5.229%	$60.6435	$60.64	$60.65	$60.60
Purchase #6	$99.47	4.111%	$103.5592	$103.56	$103.55	$103.60
Purchase #7	$45.81	4.578%	$47.9072	$47.91	$47.90	$47.90
7 purchase totals =	$826.19		$907.5492	$907.54	$907.55	$907.60