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	$165.34	4.160%	$172.2181	$172.22	$172.20	$172.20
Purchase #2	$164.56	10.121%	$181.2151	$181.22	$181.20	$181.20
Purchase #3	$142.73	12.625%	$160.7497	$160.75	$160.75	$160.70
Purchase #4	$62.90	5.347%	$66.2633	$66.26	$66.25	$66.30
Purchase #5	$242.82	11.843%	$271.5772	$271.58	$271.60	$271.60
Purchase #6	$37.53	7.137%	$40.2085	$40.21	$40.20	$40.20
Purchase #7	$212.53	13.318%	$240.8347	$240.83	$240.85	$240.80
7 purchase totals =	$1,028.41		$1,133.0666	$1,133.07	$1,133.05	$1,133.00