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	$125.97	4.350%	$131.4497	$131.45	$131.45	$131.40
Purchase #2	$17.94	12.167%	$20.1228	$20.12	$20.10	$20.10
Purchase #3	$40.51	5.806%	$42.862	$42.86	$42.85	$42.90
Purchase #4	$105.76	4.339%	$110.3489	$110.35	$110.35	$110.30
Purchase #5	$33.35	10.471%	$36.8421	$36.84	$36.85	$36.80
Purchase #6	$158.25	9.206%	$172.8185	$172.82	$172.80	$172.80
Purchase #7	$181.36	8.421%	$196.6323	$196.63	$196.65	$196.60
7 purchase totals =	$663.14		$711.0763	$711.07	$711.05	$710.90