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	$208.71	10.806%	$231.2632	$231.26	$231.25	$231.30
Purchase #2	$54.78	9.482%	$59.9742	$59.97	$59.95	$60.00
Purchase #3	$78.40	13.624%	$89.0812	$89.08	$89.10	$89.10
Purchase #4	$238.34	12.381%	$267.8489	$267.85	$267.85	$267.80
Purchase #5	$89.86	8.802%	$97.7695	$97.77	$97.75	$97.80
Purchase #6	$69.56	9.693%	$76.3025	$76.30	$76.30	$76.30
Purchase #7	$108.90	7.391%	$116.9488	$116.95	$116.95	$116.90
7 purchase totals =	$848.55		$939.1883	$939.18	$939.15	$939.20