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	$101.82	9.224%	$111.2119	$111.21	$111.20	$111.20
Purchase #2	$156.47	5.560%	$165.1697	$165.17	$165.15	$165.20
Purchase #3	$186.84	9.135%	$203.9078	$203.91	$203.90	$203.90
Purchase #4	$127.83	8.872%	$139.1711	$139.17	$139.15	$139.20
Purchase #5	$202.78	7.770%	$218.536	$218.54	$218.55	$218.50
Purchase #6	$41.68	4.520%	$43.5639	$43.56	$43.55	$43.60
Purchase #7	$237.76	12.314%	$267.0378	$267.04	$267.05	$267.00
7 purchase totals =	$1,055.18		$1,148.5982	$1,148.60	$1,148.55	$1,148.60