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	$211.82	4.224%	$220.7673	$220.77	$220.75	$220.80
Purchase #2	$89.28	8.325%	$96.7126	$96.71	$96.70	$96.70
Purchase #3	$48.91	11.137%	$54.3571	$54.36	$54.35	$54.40
Purchase #4	$166.88	12.686%	$188.0504	$188.05	$188.05	$188.10
Purchase #5	$209.25	7.694%	$225.3497	$225.35	$225.35	$225.30
Purchase #6	$74.45	4.836%	$78.0504	$78.05	$78.05	$78.10
Purchase #7	$67.30	6.462%	$71.6489	$71.65	$71.65	$71.60
7 purchase totals =	$867.89		$934.9364	$934.94	$934.90	$935.00