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	$86.97	12.376%	$97.7334	$97.73	$97.75	$97.70
Purchase #2	$88.92	12.506%	$100.0403	$100.04	$100.05	$100.00
Purchase #3	$109.68	8.593%	$119.1048	$119.10	$119.10	$119.10
Purchase #4	$137.25	10.814%	$152.0922	$152.09	$152.10	$152.10
Purchase #5	$137.77	11.345%	$153.4	$153.40	$153.40	$153.40
Purchase #6	$29.46	13.178%	$33.3422	$33.34	$33.35	$33.30
Purchase #7	$45.50	11.691%	$50.8194	$50.82	$50.80	$50.80
7 purchase totals =	$635.55		$706.5323	$706.52	$706.55	$706.40