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	$101.39	10.219%	$111.751	$111.75	$111.75	$111.80
Purchase #2	$236.27	7.715%	$254.4982	$254.50	$254.50	$254.50
Purchase #3	$103.30	6.449%	$109.9618	$109.96	$109.95	$110.00
Purchase #4	$9.94	11.861%	$11.119	$11.12	$11.10	$11.10
Purchase #5	$218.45	5.755%	$231.0218	$231.02	$231.00	$231.00
Purchase #6	$63.96	11.363%	$71.2278	$71.23	$71.25	$71.20
Purchase #7	$159.49	5.156%	$167.7133	$167.71	$167.70	$167.70
7 purchase totals =	$892.80		$957.2929	$957.29	$957.25	$957.30