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	$98.29	12.787%	$110.8583	$110.86	$110.85	$110.90
Purchase #2	$150.89	12.281%	$169.4208	$169.42	$169.40	$169.40
Purchase #3	$82.52	6.118%	$87.5686	$87.57	$87.55	$87.60
Purchase #4	$78.71	5.768%	$83.25	$83.25	$83.25	$83.30
Purchase #5	$44.99	7.749%	$48.4763	$48.48	$48.50	$48.50
Purchase #6	$51.75	8.830%	$56.3195	$56.32	$56.30	$56.30
Purchase #7	$146.60	4.246%	$152.8246	$152.82	$152.80	$152.80
7 purchase totals =	$653.75		$708.7181	$708.72	$708.65	$708.80