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	$98.69	12.597%	$111.122	$111.12	$111.10	$111.10
Purchase #2	$178.58	3.322%	$184.5124	$184.51	$184.50	$184.50
Purchase #3	$44.40	10.817%	$49.2027	$49.20	$49.20	$49.20
Purchase #4	$123.33	13.422%	$139.8834	$139.88	$139.90	$139.90
Purchase #5	$9.33	13.524%	$10.5918	$10.59	$10.60	$10.60
Purchase #6	$127.32	7.322%	$136.6424	$136.64	$136.65	$136.60
Purchase #7	$91.60	3.266%	$94.5917	$94.59	$94.60	$94.60
7 purchase totals =	$673.25		$726.5464	$726.53	$726.55	$726.50