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	$32.43	4.388%	$33.853	$33.85	$33.85	$33.90
Purchase #2	$154.28	9.848%	$169.4735	$169.47	$169.45	$169.50
Purchase #3	$167.34	13.528%	$189.9778	$189.98	$190.00	$190.00
Purchase #4	$82.81	10.595%	$91.5837	$91.58	$91.60	$91.60
Purchase #5	$211.43	7.404%	$227.0843	$227.08	$227.10	$227.10
Purchase #6	$238.81	3.638%	$247.4979	$247.50	$247.50	$247.50
Purchase #7	$123.96	7.630%	$133.4181	$133.42	$133.40	$133.40
7 purchase totals =	$1,011.06		$1,092.8883	$1,092.88	$1,092.90	$1,093.00