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	$71.31	5.299%	$75.0887	$75.09	$75.10	$75.10
Purchase #2	$222.59	13.862%	$253.4454	$253.45	$253.45	$253.40
Purchase #3	$143.55	6.204%	$152.4558	$152.46	$152.45	$152.50
Purchase #4	$47.31	4.287%	$49.3382	$49.34	$49.35	$49.30
Purchase #5	$148.46	6.154%	$157.5962	$157.60	$157.60	$157.60
Purchase #6	$242.46	8.790%	$263.7722	$263.77	$263.75	$263.80
Purchase #7	$176.39	11.604%	$196.8583	$196.86	$196.85	$196.90
7 purchase totals =	$1,052.07		$1,148.5548	$1,148.57	$1,148.55	$1,148.60