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	$76.56	8.631%	$83.1679	$83.17	$83.15	$83.20
Purchase #2	$40.90	10.110%	$45.035	$45.04	$45.05	$45.00
Purchase #3	$80.80	6.208%	$85.8161	$85.82	$85.80	$85.80
Purchase #4	$53.47	11.787%	$59.7725	$59.77	$59.75	$59.80
Purchase #5	$214.97	13.300%	$243.561	$243.56	$243.55	$243.60
Purchase #6	$155.58	7.553%	$167.331	$167.33	$167.35	$167.30
Purchase #7	$67.84	8.576%	$73.658	$73.66	$73.65	$73.70
7 purchase totals =	$690.12		$758.3415	$758.35	$758.30	$758.40