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	$153.27	3.156%	$158.1072	$158.11	$158.10	$158.10
Purchase #2	$215.72	7.816%	$232.5807	$232.58	$232.60	$232.60
Purchase #3	$145.82	8.281%	$157.8954	$157.90	$157.90	$157.90
Purchase #4	$220.72	3.283%	$227.9662	$227.97	$227.95	$228.00
Purchase #5	$122.27	7.561%	$131.5148	$131.51	$131.50	$131.50
Purchase #6	$227.94	12.123%	$255.5732	$255.57	$255.55	$255.60
Purchase #7	$93.41	7.112%	$100.0533	$100.05	$100.05	$100.10
7 purchase totals =	$1,179.15		$1,263.6908	$1,263.69	$1,263.65	$1,263.80