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	$122.91	6.473%	$130.866	$130.87	$130.85	$130.90
Purchase #2	$227.63	4.807%	$238.5722	$238.57	$238.55	$238.60
Purchase #3	$98.75	4.446%	$103.1404	$103.14	$103.15	$103.10
Purchase #4	$141.52	4.742%	$148.2309	$148.23	$148.25	$148.20
Purchase #5	$86.25	4.700%	$90.3038	$90.30	$90.30	$90.30
Purchase #6	$59.34	9.599%	$65.036	$65.04	$65.05	$65.00
Purchase #7	$189.31	10.705%	$209.5756	$209.58	$209.60	$209.60
7 purchase totals =	$925.71		$985.7249	$985.73	$985.75	$985.70