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	$238.31	6.327%	$253.3879	$253.39	$253.40	$253.40
Purchase #2	$61.89	4.593%	$64.7326	$64.73	$64.75	$64.70
Purchase #3	$42.50	7.658%	$45.7547	$45.75	$45.75	$45.80
Purchase #4	$96.70	4.383%	$100.9384	$100.94	$100.95	$100.90
Purchase #5	$5.81	8.297%	$6.2921	$6.29	$6.30	$6.30
Purchase #6	$190.69	12.141%	$213.8417	$213.84	$213.85	$213.80
Purchase #7	$70.46	8.238%	$76.2645	$76.26	$76.25	$76.30
7 purchase totals =	$706.36		$761.2119	$761.20	$761.25	$761.20