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	$37.87	10.367%	$41.796	$41.80	$41.80	$41.80
Purchase #2	$89.60	11.827%	$100.197	$100.20	$100.20	$100.20
Purchase #3	$69.49	12.812%	$78.3931	$78.39	$78.40	$78.40
Purchase #4	$182.39	11.378%	$203.1423	$203.14	$203.15	$203.10
Purchase #5	$177.43	7.465%	$190.6751	$190.68	$190.70	$190.70
Purchase #6	$127.75	10.179%	$140.7537	$140.75	$140.75	$140.80
Purchase #7	$73.30	12.538%	$82.4904	$82.49	$82.50	$82.50
7 purchase totals =	$757.83		$837.4476	$837.45	$837.50	$837.50