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	$103.77	7.110%	$111.148	$111.15	$111.15	$111.10
Purchase #2	$175.71	5.539%	$185.4426	$185.44	$185.45	$185.40
Purchase #3	$47.45	11.482%	$52.8982	$52.90	$52.90	$52.90
Purchase #4	$136.80	13.199%	$154.8562	$154.86	$154.85	$154.90
Purchase #5	$246.27	7.632%	$265.0653	$265.07	$265.05	$265.10
Purchase #6	$78.58	7.178%	$84.2205	$84.22	$84.20	$84.20
Purchase #7	$95.75	8.432%	$103.8236	$103.82	$103.80	$103.80
7 purchase totals =	$884.33		$957.4544	$957.46	$957.40	$957.40