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	$172.88	8.231%	$187.1098	$187.11	$187.10	$187.10
Purchase #2	$11.67	4.752%	$12.2246	$12.22	$12.20	$12.20
Purchase #3	$15.92	11.293%	$17.7178	$17.72	$17.70	$17.70
Purchase #4	$30.33	6.491%	$32.2987	$32.30	$32.30	$32.30
Purchase #5	$148.78	13.686%	$169.142	$169.14	$169.15	$169.10
Purchase #6	$92.54	13.565%	$105.0931	$105.09	$105.10	$105.10
Purchase #7	$69.70	3.333%	$72.0231	$72.02	$72.00	$72.00
7 purchase totals =	$541.82		$595.6091	$595.60	$595.55	$595.50