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	$78.62	4.678%	$82.2978	$82.30	$82.30	$82.30
Purchase #2	$83.25	9.109%	$90.8332	$90.83	$90.85	$90.80
Purchase #3	$38.66	13.430%	$43.852	$43.85	$43.85	$43.90
Purchase #4	$224.88	8.560%	$244.1297	$244.13	$244.15	$244.10
Purchase #5	$44.85	13.587%	$50.9438	$50.94	$50.95	$50.90
Purchase #6	$57.48	3.631%	$59.5671	$59.57	$59.55	$59.60
Purchase #7	$128.80	13.463%	$146.1403	$146.14	$146.15	$146.10
7 purchase totals =	$656.54		$717.7639	$717.76	$717.80	$717.70