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	$74.33	9.282%	$81.2293	$81.23	$81.25	$81.20
Purchase #2	$240.77	4.154%	$250.7716	$250.77	$250.75	$250.80
Purchase #3	$91.39	9.863%	$100.4038	$100.40	$100.40	$100.40
Purchase #4	$174.82	11.733%	$195.3316	$195.33	$195.35	$195.30
Purchase #5	$153.66	12.148%	$172.3266	$172.33	$172.35	$172.30
Purchase #6	$168.31	10.287%	$185.624	$185.62	$185.60	$185.60
Purchase #7	$46.44	6.117%	$49.2807	$49.28	$49.30	$49.30
7 purchase totals =	$949.72		$1,034.9676	$1,034.96	$1,035.00	$1,034.90