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	$95.90	12.692%	$108.0716	$108.07	$108.05	$108.10
Purchase #2	$141.85	7.425%	$152.3824	$152.38	$152.40	$152.40
Purchase #3	$200.38	10.534%	$221.488	$221.49	$221.50	$221.50
Purchase #4	$217.25	11.736%	$242.7465	$242.75	$242.75	$242.70
Purchase #5	$31.51	6.671%	$33.612	$33.61	$33.60	$33.60
Purchase #6	$136.39	10.535%	$150.7587	$150.76	$150.75	$150.80
Purchase #7	$213.73	12.472%	$240.3864	$240.39	$240.40	$240.40
7 purchase totals =	$1,037.01		$1,149.4456	$1,149.45	$1,149.45	$1,149.50