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	$173.44	13.350%	$196.5942	$196.59	$196.60	$196.60
Purchase #2	$96.68	8.865%	$105.2507	$105.25	$105.25	$105.30
Purchase #3	$161.50	9.502%	$176.8457	$176.85	$176.85	$176.80
Purchase #4	$122.86	10.823%	$136.1571	$136.16	$136.15	$136.20
Purchase #5	$38.46	10.306%	$42.4237	$42.42	$42.40	$42.40
Purchase #6	$36.54	12.499%	$41.1071	$41.11	$41.10	$41.10
Purchase #7	$18.73	6.490%	$19.9456	$19.95	$19.95	$19.90
7 purchase totals =	$648.21		$718.3241	$718.33	$718.30	$718.30