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	$53.96	10.520%	$59.6366	$59.64	$59.65	$59.60
Purchase #2	$136.42	7.584%	$146.7661	$146.77	$146.75	$146.80
Purchase #3	$119.41	4.142%	$124.356	$124.36	$124.35	$124.40
Purchase #4	$192.68	10.596%	$213.0964	$213.10	$213.10	$213.10
Purchase #5	$130.75	5.437%	$137.8589	$137.86	$137.85	$137.90
Purchase #6	$100.51	7.306%	$107.8533	$107.85	$107.85	$107.90
Purchase #7	$200.82	8.498%	$217.8857	$217.89	$217.90	$217.90
7 purchase totals =	$934.55		$1,007.4530	$1,007.47	$1,007.45	$1,007.60