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	$186.95	7.150%	$200.3169	$200.32	$200.30	$200.30
Purchase #2	$65.56	10.160%	$72.2209	$72.22	$72.20	$72.20
Purchase #3	$21.72	5.114%	$22.8308	$22.83	$22.85	$22.80
Purchase #4	$170.93	5.776%	$180.8029	$180.80	$180.80	$180.80
Purchase #5	$131.82	12.527%	$148.3331	$148.33	$148.35	$148.30
Purchase #6	$74.71	9.622%	$81.8986	$81.90	$81.90	$81.90
Purchase #7	$5.74	7.644%	$6.1788	$6.18	$6.20	$6.20
7 purchase totals =	$657.43		$712.5820	$712.58	$712.60	$712.50