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	$182.44	7.523%	$196.165	$196.17	$196.15	$196.20
Purchase #2	$230.31	12.813%	$259.8196	$259.82	$259.80	$259.80
Purchase #3	$143.95	12.380%	$161.771	$161.77	$161.75	$161.80
Purchase #4	$122.58	8.798%	$133.3646	$133.36	$133.35	$133.40
Purchase #5	$29.73	5.665%	$31.4142	$31.41	$31.40	$31.40
Purchase #6	$33.31	13.525%	$37.8152	$37.82	$37.80	$37.80
Purchase #7	$202.64	10.182%	$223.2728	$223.27	$223.25	$223.30
7 purchase totals =	$944.96		$1,043.6224	$1,043.62	$1,043.50	$1,043.70