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	$118.56	10.294%	$130.7646	$130.76	$130.75	$130.80
Purchase #2	$215.75	11.743%	$241.0855	$241.09	$241.10	$241.10
Purchase #3	$28.54	11.606%	$31.8524	$31.85	$31.85	$31.90
Purchase #4	$188.76	8.677%	$205.1387	$205.14	$205.15	$205.10
Purchase #5	$68.52	5.154%	$72.0515	$72.05	$72.05	$72.10
Purchase #6	$117.48	11.158%	$130.5884	$130.59	$130.60	$130.60
Purchase #7	$57.51	7.811%	$62.0021	$62.00	$62.00	$62.00
7 purchase totals =	$795.12		$873.4832	$873.48	$873.50	$873.60