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	$152.61	11.324%	$169.8916	$169.89	$169.90	$169.90
Purchase #2	$18.66	6.870%	$19.9419	$19.94	$19.95	$19.90
Purchase #3	$221.98	4.830%	$232.7016	$232.70	$232.70	$232.70
Purchase #4	$132.94	11.535%	$148.2746	$148.27	$148.25	$148.30
Purchase #5	$188.29	6.165%	$199.8981	$199.90	$199.90	$199.90
Purchase #6	$134.97	11.370%	$150.3161	$150.32	$150.30	$150.30
Purchase #7	$130.55	10.680%	$144.4927	$144.49	$144.50	$144.50
7 purchase totals =	$980.00		$1,065.5166	$1,065.51	$1,065.50	$1,065.50