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	$201.91	10.392%	$222.8925	$222.89	$222.90	$222.90
Purchase #2	$199.58	11.462%	$222.4559	$222.46	$222.45	$222.50
Purchase #3	$92.37	6.428%	$98.3075	$98.31	$98.30	$98.30
Purchase #4	$154.39	9.626%	$169.2516	$169.25	$169.25	$169.30
Purchase #5	$80.83	5.628%	$85.3791	$85.38	$85.40	$85.40
Purchase #6	$78.57	11.604%	$87.6873	$87.69	$87.70	$87.70
Purchase #7	$62.51	11.438%	$69.6599	$69.66	$69.65	$69.70
7 purchase totals =	$870.16		$955.6338	$955.64	$955.65	$955.80