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	$202.86	6.183%	$215.4028	$215.40	$215.40	$215.40
Purchase #2	$40.81	3.490%	$42.2343	$42.23	$42.25	$42.20
Purchase #3	$37.71	10.779%	$41.7748	$41.77	$41.75	$41.80
Purchase #4	$110.27	5.638%	$116.487	$116.49	$116.50	$116.50
Purchase #5	$18.88	5.538%	$19.9256	$19.93	$19.95	$19.90
Purchase #6	$42.64	7.321%	$45.7617	$45.76	$45.75	$45.80
Purchase #7	$180.76	5.765%	$191.1808	$191.18	$191.20	$191.20
7 purchase totals =	$633.93		$672.7670	$672.76	$672.80	$672.80