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	$194.46	11.449%	$216.7237	$216.72	$216.70	$216.70
Purchase #2	$172.48	10.432%	$190.4731	$190.47	$190.45	$190.50
Purchase #3	$89.96	13.241%	$101.8716	$101.87	$101.85	$101.90
Purchase #4	$221.74	8.563%	$240.7276	$240.73	$240.75	$240.70
Purchase #5	$182.45	7.704%	$196.5059	$196.51	$196.50	$196.50
Purchase #6	$145.44	4.208%	$151.5601	$151.56	$151.55	$151.60
Purchase #7	$136.92	7.588%	$147.3095	$147.31	$147.30	$147.30
7 purchase totals =	$1,143.45		$1,245.1715	$1,245.17	$1,245.10	$1,245.20