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	$125.76	6.134%	$133.4741	$133.47	$133.45	$133.50
Purchase #2	$145.97	5.814%	$154.4567	$154.46	$154.45	$154.50
Purchase #3	$38.65	13.391%	$43.8256	$43.83	$43.85	$43.80
Purchase #4	$37.69	13.834%	$42.904	$42.90	$42.90	$42.90
Purchase #5	$205.70	12.576%	$231.5688	$231.57	$231.55	$231.60
Purchase #6	$144.85	11.127%	$160.9675	$160.97	$160.95	$161.00
Purchase #7	$221.37	9.613%	$242.6503	$242.65	$242.65	$242.70
7 purchase totals =	$919.99		$1,009.8470	$1,009.85	$1,009.80	$1,010.00