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	$32.65	13.667%	$37.1123	$37.11	$37.10	$37.10
Purchase #2	$98.90	12.383%	$111.1468	$111.15	$111.15	$111.10
Purchase #3	$104.57	10.383%	$115.4275	$115.43	$115.45	$115.40
Purchase #4	$187.85	12.822%	$211.9361	$211.94	$211.95	$211.90
Purchase #5	$141.85	12.226%	$159.1926	$159.19	$159.20	$159.20
Purchase #6	$166.95	3.180%	$172.259	$172.26	$172.25	$172.30
Purchase #7	$163.46	5.447%	$172.3637	$172.36	$172.35	$172.40
7 purchase totals =	$896.23		$979.4380	$979.44	$979.45	$979.40