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	$131.89	7.622%	$141.9427	$141.94	$141.95	$141.90
Purchase #2	$113.29	12.864%	$127.8636	$127.86	$127.85	$127.90
Purchase #3	$115.70	3.847%	$120.151	$120.15	$120.15	$120.20
Purchase #4	$172.90	13.541%	$196.3124	$196.31	$196.30	$196.30
Purchase #5	$214.44	4.780%	$224.6902	$224.69	$224.70	$224.70
Purchase #6	$67.30	11.175%	$74.8208	$74.82	$74.80	$74.80
Purchase #7	$36.68	12.750%	$41.3567	$41.36	$41.35	$41.40
7 purchase totals =	$852.20		$927.1374	$927.13	$927.10	$927.20