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	$180.59	8.619%	$196.1551	$196.16	$196.15	$196.20
Purchase #2	$190.61	4.871%	$199.8946	$199.89	$199.90	$199.90
Purchase #3	$37.92	11.689%	$42.3525	$42.35	$42.35	$42.40
Purchase #4	$78.64	5.362%	$82.8567	$82.86	$82.85	$82.90
Purchase #5	$41.31	8.548%	$44.8412	$44.84	$44.85	$44.80
Purchase #6	$59.51	3.150%	$61.3846	$61.38	$61.40	$61.40
Purchase #7	$131.85	6.374%	$140.2541	$140.25	$140.25	$140.30
7 purchase totals =	$720.43		$767.7388	$767.73	$767.75	$767.90