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	$137.56	7.742%	$148.2099	$148.21	$148.20	$148.20
Purchase #2	$104.30	12.455%	$117.2906	$117.29	$117.30	$117.30
Purchase #3	$32.94	12.815%	$37.1613	$37.16	$37.15	$37.20
Purchase #4	$126.39	12.655%	$142.3847	$142.38	$142.40	$142.40
Purchase #5	$169.50	10.197%	$186.7839	$186.78	$186.80	$186.80
Purchase #6	$145.63	5.327%	$153.3877	$153.39	$153.40	$153.40
Purchase #7	$182.59	4.144%	$190.1565	$190.16	$190.15	$190.20
7 purchase totals =	$898.91		$975.3746	$975.37	$975.40	$975.50