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	$100.61	12.577%	$113.2637	$113.26	$113.25	$113.30
Purchase #2	$200.50	4.456%	$209.4343	$209.43	$209.45	$209.40
Purchase #3	$191.82	3.519%	$198.5701	$198.57	$198.55	$198.60
Purchase #4	$50.51	8.664%	$54.8862	$54.89	$54.90	$54.90
Purchase #5	$48.94	3.359%	$50.5839	$50.58	$50.60	$50.60
Purchase #6	$41.77	8.466%	$45.3062	$45.31	$45.30	$45.30
Purchase #7	$175.64	3.695%	$182.1299	$182.13	$182.15	$182.10
7 purchase totals =	$809.79		$854.1743	$854.17	$854.20	$854.20