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	$168.28	7.249%	$180.4786	$180.48	$180.50	$180.50
Purchase #2	$70.83	11.683%	$79.1051	$79.11	$79.10	$79.10
Purchase #3	$107.38	11.635%	$119.8737	$119.87	$119.85	$119.90
Purchase #4	$59.48	13.108%	$67.2766	$67.28	$67.30	$67.30
Purchase #5	$212.88	5.182%	$223.9114	$223.91	$223.90	$223.90
Purchase #6	$179.34	11.208%	$199.4404	$199.44	$199.45	$199.40
Purchase #7	$86.68	9.741%	$95.1235	$95.12	$95.10	$95.10
7 purchase totals =	$884.87		$965.2093	$965.21	$965.20	$965.20