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	$201.53	8.232%	$218.1199	$218.12	$218.10	$218.10
Purchase #2	$86.64	4.323%	$90.3854	$90.39	$90.40	$90.40
Purchase #3	$52.72	12.482%	$59.3005	$59.30	$59.30	$59.30
Purchase #4	$100.51	8.768%	$109.3227	$109.32	$109.30	$109.30
Purchase #5	$67.75	4.673%	$70.916	$70.92	$70.90	$70.90
Purchase #6	$216.26	7.733%	$232.9834	$232.98	$233.00	$233.00
Purchase #7	$121.45	6.705%	$129.5932	$129.59	$129.60	$129.60
7 purchase totals =	$846.86		$910.6211	$910.62	$910.60	$910.60