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	$169.30	12.674%	$190.7571	$190.76	$190.75	$190.80
Purchase #2	$30.88	4.492%	$32.2671	$32.27	$32.25	$32.30
Purchase #3	$233.80	6.228%	$248.3611	$248.36	$248.35	$248.40
Purchase #4	$239.54	10.398%	$264.4474	$264.45	$264.45	$264.40
Purchase #5	$187.46	5.211%	$197.2285	$197.23	$197.25	$197.20
Purchase #6	$244.51	4.590%	$255.733	$255.73	$255.75	$255.70
Purchase #7	$130.83	11.176%	$145.4516	$145.45	$145.45	$145.50
7 purchase totals =	$1,236.32		$1,334.2458	$1,334.25	$1,334.25	$1,334.30