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	$153.49	13.344%	$173.9717	$173.97	$173.95	$174.00
Purchase #2	$38.66	5.620%	$40.8327	$40.83	$40.85	$40.80
Purchase #3	$146.30	13.596%	$166.1909	$166.19	$166.20	$166.20
Purchase #4	$67.82	5.315%	$71.4246	$71.42	$71.40	$71.40
Purchase #5	$231.82	11.818%	$259.2165	$259.22	$259.20	$259.20
Purchase #6	$247.82	6.456%	$263.8193	$263.82	$263.80	$263.80
Purchase #7	$60.29	11.396%	$67.1606	$67.16	$67.15	$67.20
7 purchase totals =	$946.20		$1,042.6163	$1,042.61	$1,042.55	$1,042.60