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	$115.26	4.179%	$120.0767	$120.08	$120.10	$120.10
Purchase #2	$196.94	5.733%	$208.2306	$208.23	$208.25	$208.20
Purchase #3	$53.87	10.155%	$59.3405	$59.34	$59.35	$59.30
Purchase #4	$112.80	9.484%	$123.498	$123.50	$123.50	$123.50
Purchase #5	$216.91	11.548%	$241.9588	$241.96	$241.95	$242.00
Purchase #6	$129.62	6.371%	$137.8781	$137.88	$137.90	$137.90
Purchase #7	$52.51	11.593%	$58.5975	$58.60	$58.60	$58.60
7 purchase totals =	$877.91		$949.5802	$949.59	$949.65	$949.60