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	$229.52	12.766%	$258.8205	$258.82	$258.80	$258.80
Purchase #2	$143.42	4.681%	$150.1335	$150.13	$150.15	$150.10
Purchase #3	$196.55	7.521%	$211.3325	$211.33	$211.35	$211.30
Purchase #4	$48.56	4.425%	$50.7088	$50.71	$50.70	$50.70
Purchase #5	$75.90	9.846%	$83.3731	$83.37	$83.35	$83.40
Purchase #6	$85.33	7.318%	$91.5744	$91.57	$91.55	$91.60
Purchase #7	$193.64	11.635%	$216.17	$216.17	$216.15	$216.20
7 purchase totals =	$972.92		$1,062.1128	$1,062.10	$1,062.05	$1,062.10