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	$67.27	5.686%	$71.095	$71.10	$71.10	$71.10
Purchase #2	$200.29	11.480%	$223.2833	$223.28	$223.30	$223.30
Purchase #3	$151.53	11.421%	$168.8362	$168.84	$168.85	$168.80
Purchase #4	$221.96	9.682%	$243.4502	$243.45	$243.45	$243.50
Purchase #5	$43.79	11.724%	$48.9239	$48.92	$48.90	$48.90
Purchase #6	$90.51	11.247%	$100.6897	$100.69	$100.70	$100.70
Purchase #7	$217.80	5.745%	$230.3126	$230.31	$230.30	$230.30
7 purchase totals =	$993.15		$1,086.5909	$1,086.59	$1,086.60	$1,086.60