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	$84.97	12.289%	$95.412	$95.41	$95.40	$95.40
Purchase #2	$216.94	4.121%	$225.8801	$225.88	$225.90	$225.90
Purchase #3	$91.69	9.863%	$100.7334	$100.73	$100.75	$100.70
Purchase #4	$146.32	3.580%	$151.5583	$151.56	$151.55	$151.60
Purchase #5	$137.81	10.451%	$152.2125	$152.21	$152.20	$152.20
Purchase #6	$206.54	11.589%	$230.4759	$230.48	$230.50	$230.50
Purchase #7	$210.34	9.385%	$230.0804	$230.08	$230.10	$230.10
7 purchase totals =	$1,094.61		$1,186.3526	$1,186.35	$1,186.40	$1,186.40