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	$29.95	8.510%	$32.4987	$32.50	$32.50	$32.50
Purchase #2	$112.72	12.681%	$127.014	$127.01	$127.00	$127.00
Purchase #3	$167.53	5.548%	$176.8246	$176.82	$176.80	$176.80
Purchase #4	$140.91	6.552%	$150.1424	$150.14	$150.15	$150.10
Purchase #5	$124.44	12.162%	$139.5744	$139.57	$139.55	$139.60
Purchase #6	$8.72	9.345%	$9.5349	$9.53	$9.55	$9.50
Purchase #7	$162.92	11.535%	$181.7128	$181.71	$181.70	$181.70
7 purchase totals =	$747.19		$817.3018	$817.28	$817.25	$817.20