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	$52.40	13.759%	$59.6097	$59.61	$59.60	$59.60
Purchase #2	$52.67	13.187%	$59.6156	$59.62	$59.60	$59.60
Purchase #3	$182.83	3.317%	$188.8945	$188.89	$188.90	$188.90
Purchase #4	$148.95	13.740%	$169.4157	$169.42	$169.40	$169.40
Purchase #5	$131.33	6.693%	$140.1199	$140.12	$140.10	$140.10
Purchase #6	$227.87	8.772%	$247.8588	$247.86	$247.85	$247.90
Purchase #7	$86.89	7.759%	$93.6318	$93.63	$93.65	$93.60
7 purchase totals =	$882.94		$959.1460	$959.15	$959.10	$959.10