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	$92.56	8.751%	$100.6599	$100.66	$100.65	$100.70
Purchase #2	$42.34	12.201%	$47.5059	$47.51	$47.50	$47.50
Purchase #3	$22.78	12.291%	$25.5799	$25.58	$25.60	$25.60
Purchase #4	$236.79	9.291%	$258.7902	$258.79	$258.80	$258.80
Purchase #5	$209.69	3.237%	$216.4777	$216.48	$216.50	$216.50
Purchase #6	$162.67	11.306%	$181.0615	$181.06	$181.05	$181.10
Purchase #7	$209.66	10.448%	$231.5653	$231.57	$231.55	$231.60
7 purchase totals =	$976.49		$1,061.6404	$1,061.65	$1,061.65	$1,061.80