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	$11.54	10.269%	$12.725	$12.73	$12.75	$12.70
Purchase #2	$134.33	3.804%	$139.4399	$139.44	$139.45	$139.40
Purchase #3	$139.91	12.300%	$157.1189	$157.12	$157.10	$157.10
Purchase #4	$87.30	3.613%	$90.4541	$90.45	$90.45	$90.50
Purchase #5	$207.72	12.189%	$233.039	$233.04	$233.05	$233.00
Purchase #6	$247.29	5.803%	$261.6402	$261.64	$261.65	$261.60
Purchase #7	$203.56	12.427%	$228.8564	$228.86	$228.85	$228.90
7 purchase totals =	$1,031.65		$1,123.2735	$1,123.28	$1,123.30	$1,123.20