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	$128.48	3.389%	$132.8342	$132.83	$132.85	$132.80
Purchase #2	$132.73	8.181%	$143.5886	$143.59	$143.60	$143.60
Purchase #3	$239.70	4.439%	$250.3403	$250.34	$250.35	$250.30
Purchase #4	$130.34	12.408%	$146.5126	$146.51	$146.50	$146.50
Purchase #5	$209.82	3.735%	$217.6568	$217.66	$217.65	$217.70
Purchase #6	$30.59	8.661%	$33.2394	$33.24	$33.25	$33.20
Purchase #7	$195.91	3.565%	$202.8942	$202.89	$202.90	$202.90
7 purchase totals =	$1,067.57		$1,127.0661	$1,127.06	$1,127.10	$1,127.00