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	$56.81	4.842%	$59.5607	$59.56	$59.55	$59.60
Purchase #2	$145.27	13.131%	$164.3454	$164.35	$164.35	$164.30
Purchase #3	$120.98	12.491%	$136.0916	$136.09	$136.10	$136.10
Purchase #4	$201.80	11.166%	$224.333	$224.33	$224.35	$224.30
Purchase #5	$164.65	10.438%	$181.8362	$181.84	$181.85	$181.80
Purchase #6	$160.47	12.186%	$180.0249	$180.02	$180.00	$180.00
Purchase #7	$35.58	9.435%	$38.937	$38.94	$38.95	$38.90
7 purchase totals =	$885.56		$985.1288	$985.13	$985.15	$985.00