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	$94.60	4.476%	$98.8343	$98.83	$98.85	$98.80
Purchase #2	$33.95	4.516%	$35.4832	$35.48	$35.50	$35.50
Purchase #3	$201.83	7.614%	$217.1973	$217.20	$217.20	$217.20
Purchase #4	$6.61	5.276%	$6.9587	$6.96	$6.95	$7.00
Purchase #5	$39.85	5.662%	$42.1063	$42.11	$42.10	$42.10
Purchase #6	$64.64	12.652%	$72.8183	$72.82	$72.80	$72.80
Purchase #7	$57.54	5.818%	$60.8877	$60.89	$60.90	$60.90
7 purchase totals =	$499.02		$534.2858	$534.29	$534.30	$534.30