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	$117.50	12.789%	$132.5271	$132.53	$132.55	$132.50
Purchase #2	$85.30	5.300%	$89.8209	$89.82	$89.80	$89.80
Purchase #3	$145.74	12.513%	$163.9764	$163.98	$164.00	$164.00
Purchase #4	$210.28	3.687%	$218.033	$218.03	$218.05	$218.00
Purchase #5	$203.83	6.388%	$216.8507	$216.85	$216.85	$216.90
Purchase #6	$39.72	13.775%	$45.1914	$45.19	$45.20	$45.20
Purchase #7	$243.81	8.594%	$264.763	$264.76	$264.75	$264.80
7 purchase totals =	$1,046.18		$1,131.1625	$1,131.16	$1,131.20	$1,131.20