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	$147.72	8.382%	$160.1019	$160.10	$160.10	$160.10
Purchase #2	$8.50	9.434%	$9.3019	$9.30	$9.30	$9.30
Purchase #3	$39.27	8.702%	$42.6873	$42.69	$42.70	$42.70
Purchase #4	$39.99	8.564%	$43.4147	$43.41	$43.40	$43.40
Purchase #5	$111.79	10.729%	$123.7839	$123.78	$123.80	$123.80
Purchase #6	$225.55	13.306%	$255.5617	$255.56	$255.55	$255.60
Purchase #7	$149.34	11.792%	$166.9502	$166.95	$166.95	$167.00
7 purchase totals =	$722.16		$801.8016	$801.79	$801.80	$801.90