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	$245.48	4.315%	$256.0725	$256.07	$256.05	$256.10
Purchase #2	$90.88	9.642%	$99.6426	$99.64	$99.65	$99.60
Purchase #3	$28.53	10.248%	$31.4538	$31.45	$31.45	$31.50
Purchase #4	$206.37	9.365%	$225.6966	$225.70	$225.70	$225.70
Purchase #5	$162.33	10.224%	$178.9266	$178.93	$178.95	$178.90
Purchase #6	$54.69	10.668%	$60.5243	$60.52	$60.50	$60.50
Purchase #7	$104.63	9.814%	$114.8984	$114.90	$114.90	$114.90
7 purchase totals =	$892.91		$967.2148	$967.21	$967.20	$967.20