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	$34.86	4.586%	$36.4587	$36.46	$36.45	$36.50
Purchase #2	$200.31	13.591%	$227.5341	$227.53	$227.55	$227.50
Purchase #3	$133.67	12.670%	$150.606	$150.61	$150.60	$150.60
Purchase #4	$214.40	8.180%	$231.9379	$231.94	$231.95	$231.90
Purchase #5	$91.58	4.787%	$95.9639	$95.96	$95.95	$96.00
Purchase #6	$46.48	6.694%	$49.5914	$49.59	$49.60	$49.60
Purchase #7	$199.55	5.746%	$211.0161	$211.02	$211.00	$211.00
7 purchase totals =	$920.85		$1,003.1081	$1,003.11	$1,003.10	$1,003.10