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	$90.28	7.481%	$97.0338	$97.03	$97.05	$97.00
Purchase #2	$92.39	9.230%	$100.9176	$100.92	$100.90	$100.90
Purchase #3	$132.72	6.648%	$141.5432	$141.54	$141.55	$141.50
Purchase #4	$88.96	3.611%	$92.1723	$92.17	$92.15	$92.20
Purchase #5	$83.50	3.256%	$86.2188	$86.22	$86.20	$86.20
Purchase #6	$197.62	11.166%	$219.6862	$219.69	$219.70	$219.70
Purchase #7	$20.98	4.265%	$21.8748	$21.87	$21.85	$21.90
7 purchase totals =	$706.45		$759.4467	$759.44	$759.40	$759.40