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	$7.56	4.153%	$7.874	$7.87	$7.85	$7.90
Purchase #2	$222.51	9.812%	$244.3427	$244.34	$244.35	$244.30
Purchase #3	$135.66	11.617%	$151.4196	$151.42	$151.40	$151.40
Purchase #4	$13.61	13.595%	$15.4603	$15.46	$15.45	$15.50
Purchase #5	$28.53	5.501%	$30.0994	$30.10	$30.10	$30.10
Purchase #6	$13.96	13.626%	$15.8622	$15.86	$15.85	$15.90
Purchase #7	$139.82	7.874%	$150.8294	$150.83	$150.85	$150.80
7 purchase totals =	$561.65		$615.8876	$615.88	$615.85	$615.90