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	$185.93	10.187%	$204.8707	$204.87	$204.85	$204.90
Purchase #2	$85.43	6.321%	$90.83	$90.83	$90.85	$90.80
Purchase #3	$41.95	10.200%	$46.2289	$46.23	$46.25	$46.20
Purchase #4	$39.95	13.627%	$45.394	$45.39	$45.40	$45.40
Purchase #5	$229.76	6.313%	$244.2647	$244.26	$244.25	$244.30
Purchase #6	$23.72	8.307%	$25.6904	$25.69	$25.70	$25.70
Purchase #7	$217.61	7.473%	$233.872	$233.87	$233.85	$233.90
7 purchase totals =	$824.35		$891.1507	$891.14	$891.15	$891.20