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	$98.87	10.106%	$108.8618	$108.86	$108.85	$108.90
Purchase #2	$132.48	6.573%	$141.1879	$141.19	$141.20	$141.20
Purchase #3	$218.30	12.182%	$244.8933	$244.89	$244.90	$244.90
Purchase #4	$53.67	10.480%	$59.2946	$59.29	$59.30	$59.30
Purchase #5	$137.67	8.259%	$149.0402	$149.04	$149.05	$149.00
Purchase #6	$241.81	13.209%	$273.7507	$273.75	$273.75	$273.80
Purchase #7	$76.53	5.220%	$80.5249	$80.52	$80.50	$80.50
7 purchase totals =	$959.33		$1,057.5534	$1,057.54	$1,057.55	$1,057.60