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	$197.43	9.414%	$216.0161	$216.02	$216.00	$216.00
Purchase #2	$222.28	7.221%	$238.3308	$238.33	$238.35	$238.30
Purchase #3	$92.74	5.141%	$97.5078	$97.51	$97.50	$97.50
Purchase #4	$67.66	5.443%	$71.3427	$71.34	$71.35	$71.30
Purchase #5	$56.52	4.623%	$59.1329	$59.13	$59.15	$59.10
Purchase #6	$150.83	4.187%	$157.1453	$157.15	$157.15	$157.10
Purchase #7	$66.84	6.652%	$71.2862	$71.29	$71.30	$71.30
7 purchase totals =	$854.30		$910.7618	$910.77	$910.80	$910.60