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	$37.46	7.866%	$40.4066	$40.41	$40.40	$40.40
Purchase #2	$85.61	4.302%	$89.2929	$89.29	$89.30	$89.30
Purchase #3	$203.41	10.334%	$224.4304	$224.43	$224.45	$224.40
Purchase #4	$177.32	10.866%	$196.5876	$196.59	$196.60	$196.60
Purchase #5	$20.94	7.614%	$22.5344	$22.53	$22.55	$22.50
Purchase #6	$43.63	10.151%	$48.0589	$48.06	$48.05	$48.10
Purchase #7	$91.89	13.529%	$104.3218	$104.32	$104.30	$104.30
7 purchase totals =	$660.26		$725.6326	$725.63	$725.65	$725.60