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	$45.61	6.739%	$48.6837	$48.68	$48.70	$48.70
Purchase #2	$119.52	6.436%	$127.2123	$127.21	$127.20	$127.20
Purchase #3	$41.81	12.151%	$46.8903	$46.89	$46.90	$46.90
Purchase #4	$40.56	12.800%	$45.7517	$45.75	$45.75	$45.80
Purchase #5	$225.50	3.142%	$232.5852	$232.59	$232.60	$232.60
Purchase #6	$122.90	4.285%	$128.1663	$128.17	$128.15	$128.20
Purchase #7	$232.64	6.718%	$248.2688	$248.27	$248.25	$248.30
7 purchase totals =	$828.54		$877.5583	$877.56	$877.55	$877.70