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	$93.49	9.517%	$102.3874	$102.39	$102.40	$102.40
Purchase #2	$58.36	9.631%	$63.9807	$63.98	$64.00	$64.00
Purchase #3	$9.90	6.236%	$10.5174	$10.52	$10.50	$10.50
Purchase #4	$140.54	4.582%	$146.9795	$146.98	$147.00	$147.00
Purchase #5	$172.97	13.638%	$196.5596	$196.56	$196.55	$196.60
Purchase #6	$230.54	11.287%	$256.561	$256.56	$256.55	$256.60
Purchase #7	$29.76	3.762%	$30.8796	$30.88	$30.90	$30.90
7 purchase totals =	$735.56		$807.8652	$807.87	$807.90	$808.00