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	$40.56	13.246%	$45.9326	$45.93	$45.95	$45.90
Purchase #2	$80.65	13.183%	$91.2821	$91.28	$91.30	$91.30
Purchase #3	$64.44	3.185%	$66.4924	$66.49	$66.50	$66.50
Purchase #4	$120.42	9.320%	$131.6431	$131.64	$131.65	$131.60
Purchase #5	$194.82	9.516%	$213.3591	$213.36	$213.35	$213.40
Purchase #6	$131.67	11.537%	$146.8608	$146.86	$146.85	$146.90
Purchase #7	$227.42	4.110%	$236.767	$236.77	$236.75	$236.80
7 purchase totals =	$859.98		$932.3371	$932.33	$932.35	$932.40