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	$131.66	10.390%	$145.3395	$145.34	$145.35	$145.30
Purchase #2	$27.43	3.356%	$28.3506	$28.35	$28.35	$28.40
Purchase #3	$221.47	5.561%	$233.7859	$233.79	$233.80	$233.80
Purchase #4	$211.49	3.470%	$218.8287	$218.83	$218.85	$218.80
Purchase #5	$80.58	10.846%	$89.3197	$89.32	$89.30	$89.30
Purchase #6	$107.88	13.277%	$122.2032	$122.20	$122.20	$122.20
Purchase #7	$33.37	11.539%	$37.2206	$37.22	$37.20	$37.20
7 purchase totals =	$813.88		$875.0482	$875.05	$875.05	$875.00