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	$86.86	8.715%	$94.4298	$94.43	$94.45	$94.40
Purchase #2	$55.88	6.476%	$59.4988	$59.50	$59.50	$59.50
Purchase #3	$113.58	3.573%	$117.6382	$117.64	$117.65	$117.60
Purchase #4	$133.78	8.596%	$145.2797	$145.28	$145.30	$145.30
Purchase #5	$89.69	8.833%	$97.6123	$97.61	$97.60	$97.60
Purchase #6	$37.83	9.327%	$41.3584	$41.36	$41.35	$41.40
Purchase #7	$102.63	13.206%	$116.1833	$116.18	$116.20	$116.20
7 purchase totals =	$620.25		$672.0005	$672.00	$672.05	$672.00