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	$103.49	10.280%	$114.1288	$114.13	$114.15	$114.10
Purchase #2	$66.40	8.290%	$71.9046	$71.90	$71.90	$71.90
Purchase #3	$184.61	9.111%	$201.4298	$201.43	$201.45	$201.40
Purchase #4	$128.87	8.673%	$140.0469	$140.05	$140.05	$140.00
Purchase #5	$245.79	4.105%	$255.8797	$255.88	$255.90	$255.90
Purchase #6	$67.79	6.217%	$72.0045	$72.00	$72.00	$72.00
Purchase #7	$90.28	6.472%	$96.1229	$96.12	$96.10	$96.10
7 purchase totals =	$887.23		$951.5172	$951.51	$951.55	$951.40