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	$95.79	5.146%	$100.7194	$100.72	$100.70	$100.70
Purchase #2	$13.85	7.758%	$14.9245	$14.92	$14.90	$14.90
Purchase #3	$121.34	13.591%	$137.8313	$137.83	$137.85	$137.80
Purchase #4	$91.54	4.664%	$95.8094	$95.81	$95.80	$95.80
Purchase #5	$91.83	3.392%	$94.9449	$94.94	$94.95	$94.90
Purchase #6	$147.29	3.555%	$152.5262	$152.53	$152.55	$152.50
Purchase #7	$83.89	6.415%	$89.2715	$89.27	$89.25	$89.30
7 purchase totals =	$645.53		$686.0272	$686.02	$686.00	$685.90