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	$59.79	6.587%	$63.7284	$63.73	$63.75	$63.70
Purchase #2	$33.68	12.536%	$37.9021	$37.90	$37.90	$37.90
Purchase #3	$176.57	11.272%	$196.473	$196.47	$196.45	$196.50
Purchase #4	$56.44	11.805%	$63.1027	$63.10	$63.10	$63.10
Purchase #5	$203.87	10.294%	$224.8564	$224.86	$224.85	$224.90
Purchase #6	$44.84	12.807%	$50.5827	$50.58	$50.60	$50.60
Purchase #7	$85.62	7.196%	$91.7812	$91.78	$91.80	$91.80
7 purchase totals =	$660.81		$728.4265	$728.42	$728.45	$728.50