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	$208.75	6.238%	$221.7718	$221.77	$221.75	$221.80
Purchase #2	$99.90	11.572%	$111.4604	$111.46	$111.45	$111.50
Purchase #3	$214.52	13.781%	$244.083	$244.08	$244.10	$244.10
Purchase #4	$82.47	3.143%	$85.062	$85.06	$85.05	$85.10
Purchase #5	$190.50	6.845%	$203.5397	$203.54	$203.55	$203.50
Purchase #6	$129.40	10.542%	$143.0413	$143.04	$143.05	$143.00
Purchase #7	$30.96	10.539%	$34.2229	$34.22	$34.20	$34.20
7 purchase totals =	$956.50		$1,043.1811	$1,043.17	$1,043.15	$1,043.20