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	$113.31	12.298%	$127.2449	$127.24	$127.25	$127.20
Purchase #2	$83.70	12.174%	$93.8896	$93.89	$93.90	$93.90
Purchase #3	$160.61	6.688%	$171.3516	$171.35	$171.35	$171.40
Purchase #4	$33.72	3.630%	$34.944	$34.94	$34.95	$34.90
Purchase #5	$37.97	3.555%	$39.3198	$39.32	$39.30	$39.30
Purchase #6	$231.56	13.174%	$262.0657	$262.07	$262.05	$262.10
Purchase #7	$11.79	3.199%	$12.1672	$12.17	$12.15	$12.20
7 purchase totals =	$672.66		$740.9828	$740.98	$740.95	$741.00