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	$136.55	3.602%	$141.4685	$141.47	$141.45	$141.50
Purchase #2	$236.43	6.212%	$251.117	$251.12	$251.10	$251.10
Purchase #3	$224.72	9.539%	$246.156	$246.16	$246.15	$246.20
Purchase #4	$62.39	9.800%	$68.5042	$68.50	$68.50	$68.50
Purchase #5	$161.73	13.649%	$183.8045	$183.80	$183.80	$183.80
Purchase #6	$38.52	6.164%	$40.8944	$40.89	$40.90	$40.90
Purchase #7	$100.28	5.653%	$105.9488	$105.95	$105.95	$105.90
7 purchase totals =	$960.62		$1,037.8934	$1,037.89	$1,037.85	$1,037.90