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	$201.39	9.181%	$219.8796	$219.88	$219.90	$219.90
Purchase #2	$74.72	5.366%	$78.7295	$78.73	$78.75	$78.70
Purchase #3	$217.57	11.651%	$242.9191	$242.92	$242.90	$242.90
Purchase #4	$13.29	12.323%	$14.9277	$14.93	$14.95	$14.90
Purchase #5	$165.33	11.151%	$183.7659	$183.77	$183.75	$183.80
Purchase #6	$9.81	8.835%	$10.6767	$10.68	$10.70	$10.70
Purchase #7	$188.77	4.265%	$196.821	$196.82	$196.80	$196.80
7 purchase totals =	$870.88		$947.7195	$947.73	$947.75	$947.70