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	$110.36	7.198%	$118.3037	$118.30	$118.30	$118.30
Purchase #2	$63.42	12.159%	$71.1312	$71.13	$71.15	$71.10
Purchase #3	$43.81	10.667%	$48.4832	$48.48	$48.50	$48.50
Purchase #4	$78.91	8.408%	$85.5448	$85.54	$85.55	$85.50
Purchase #5	$214.96	12.373%	$241.557	$241.56	$241.55	$241.60
Purchase #6	$155.58	9.425%	$170.2434	$170.24	$170.25	$170.20
Purchase #7	$72.62	8.710%	$78.9452	$78.95	$78.95	$78.90
7 purchase totals =	$739.66		$814.2085	$814.20	$814.25	$814.10