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	$175.59	11.671%	$196.0831	$196.08	$196.10	$196.10
Purchase #2	$93.70	5.597%	$98.9444	$98.94	$98.95	$98.90
Purchase #3	$55.78	3.314%	$57.6285	$57.63	$57.65	$57.60
Purchase #4	$72.96	5.823%	$77.2085	$77.21	$77.20	$77.20
Purchase #5	$146.57	3.830%	$152.1836	$152.18	$152.20	$152.20
Purchase #6	$222.88	8.484%	$241.7891	$241.79	$241.80	$241.80
Purchase #7	$240.30	13.432%	$272.5771	$272.58	$272.60	$272.60
7 purchase totals =	$1,007.78		$1,096.4143	$1,096.41	$1,096.50	$1,096.40