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	$68.29	4.426%	$71.3125	$71.31	$71.30	$71.30
Purchase #2	$230.53	10.554%	$254.8601	$254.86	$254.85	$254.90
Purchase #3	$45.39	8.192%	$49.1083	$49.11	$49.10	$49.10
Purchase #4	$169.55	9.470%	$185.6064	$185.61	$185.60	$185.60
Purchase #5	$142.85	13.485%	$162.1133	$162.11	$162.10	$162.10
Purchase #6	$48.81	11.628%	$54.4856	$54.49	$54.50	$54.50
Purchase #7	$222.50	5.494%	$234.7242	$234.72	$234.70	$234.70
7 purchase totals =	$927.92		$1,012.2104	$1,012.21	$1,012.15	$1,012.20