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	$99.59	11.586%	$111.1285	$111.13	$111.15	$111.10
Purchase #2	$188.86	3.523%	$195.5135	$195.51	$195.50	$195.50
Purchase #3	$217.25	13.256%	$246.0487	$246.05	$246.05	$246.00
Purchase #4	$242.34	3.447%	$250.6935	$250.69	$250.70	$250.70
Purchase #5	$7.46	6.174%	$7.9206	$7.92	$7.90	$7.90
Purchase #6	$185.50	8.135%	$200.5904	$200.59	$200.60	$200.60
Purchase #7	$161.32	4.308%	$168.2697	$168.27	$168.25	$168.30
7 purchase totals =	$1,102.32		$1,180.1649	$1,180.16	$1,180.15	$1,180.10