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	$95.49	12.485%	$107.4119	$107.41	$107.40	$107.40
Purchase #2	$87.34	12.200%	$97.9955	$98.00	$98.00	$98.00
Purchase #3	$172.27	11.160%	$191.4953	$191.50	$191.50	$191.50
Purchase #4	$66.98	10.352%	$73.9138	$73.91	$73.90	$73.90
Purchase #5	$63.81	5.593%	$67.3789	$67.38	$67.40	$67.40
Purchase #6	$72.88	8.206%	$78.8605	$78.86	$78.85	$78.90
Purchase #7	$44.43	3.328%	$45.9086	$45.91	$45.90	$45.90
7 purchase totals =	$603.20		$662.9645	$662.97	$662.95	$663.00