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	$57.26	8.725%	$62.2559	$62.26	$62.25	$62.30
Purchase #2	$39.61	10.477%	$43.7599	$43.76	$43.75	$43.80
Purchase #3	$144.30	8.266%	$156.2278	$156.23	$156.25	$156.20
Purchase #4	$37.53	6.420%	$39.9394	$39.94	$39.95	$39.90
Purchase #5	$232.77	8.132%	$251.6989	$251.70	$251.70	$251.70
Purchase #6	$75.31	4.242%	$78.5047	$78.50	$78.50	$78.50
Purchase #7	$39.79	6.527%	$42.3871	$42.39	$42.40	$42.40
7 purchase totals =	$626.57		$674.7737	$674.78	$674.80	$674.80