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	$93.63	7.482%	$100.6354	$100.64	$100.65	$100.60
Purchase #2	$65.51	7.514%	$70.4324	$70.43	$70.45	$70.40
Purchase #3	$208.90	6.667%	$222.8274	$222.83	$222.85	$222.80
Purchase #4	$111.93	7.162%	$119.9464	$119.95	$119.95	$119.90
Purchase #5	$6.68	7.519%	$7.1823	$7.18	$7.20	$7.20
Purchase #6	$186.44	5.324%	$196.3661	$196.37	$196.35	$196.40
Purchase #7	$33.58	6.146%	$35.6438	$35.64	$35.65	$35.60
7 purchase totals =	$706.67		$753.0338	$753.04	$753.10	$752.90