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	$104.33	3.727%	$108.2184	$108.22	$108.20	$108.20
Purchase #2	$153.96	11.297%	$171.3529	$171.35	$171.35	$171.40
Purchase #3	$90.53	12.257%	$101.6263	$101.63	$101.65	$101.60
Purchase #4	$156.54	5.521%	$165.1826	$165.18	$165.20	$165.20
Purchase #5	$187.57	6.539%	$199.8352	$199.84	$199.85	$199.80
Purchase #6	$72.31	8.353%	$78.3501	$78.35	$78.35	$78.40
Purchase #7	$126.29	8.805%	$137.4098	$137.41	$137.40	$137.40
7 purchase totals =	$891.53		$961.9753	$961.98	$962.00	$962.00