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	$245.34	4.325%	$255.951	$255.95	$255.95	$256.00
Purchase #2	$35.46	4.298%	$36.9841	$36.98	$37.00	$37.00
Purchase #3	$90.27	8.161%	$97.6369	$97.64	$97.65	$97.60
Purchase #4	$122.96	7.255%	$131.8807	$131.88	$131.90	$131.90
Purchase #5	$64.98	4.334%	$67.7962	$67.80	$67.80	$67.80
Purchase #6	$198.30	13.403%	$224.8781	$224.88	$224.90	$224.90
Purchase #7	$246.41	8.176%	$266.5565	$266.56	$266.55	$266.60
7 purchase totals =	$1,003.72		$1,081.6835	$1,081.69	$1,081.75	$1,081.80