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	$145.82	4.379%	$152.2055	$152.21	$152.20	$152.20
Purchase #2	$196.64	10.737%	$217.7532	$217.75	$217.75	$217.80
Purchase #3	$53.94	9.634%	$59.1366	$59.14	$59.15	$59.10
Purchase #4	$165.53	4.170%	$172.4326	$172.43	$172.45	$172.40
Purchase #5	$115.38	7.502%	$124.0358	$124.04	$124.05	$124.00
Purchase #6	$37.57	10.212%	$41.4066	$41.41	$41.40	$41.40
Purchase #7	$36.89	12.170%	$41.3795	$41.38	$41.40	$41.40
7 purchase totals =	$751.77		$808.3498	$808.36	$808.40	$808.30