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	$144.40	3.458%	$149.3934	$149.39	$149.40	$149.40
Purchase #2	$140.57	11.318%	$156.4797	$156.48	$156.50	$156.50
Purchase #3	$147.67	13.484%	$167.5818	$167.58	$167.60	$167.60
Purchase #4	$129.59	8.409%	$140.4872	$140.49	$140.50	$140.50
Purchase #5	$176.29	8.446%	$191.1795	$191.18	$191.20	$191.20
Purchase #6	$43.40	7.383%	$46.6042	$46.60	$46.60	$46.60
Purchase #7	$235.86	7.630%	$253.8561	$253.86	$253.85	$253.90
7 purchase totals =	$1,017.78		$1,105.5819	$1,105.58	$1,105.65	$1,105.70