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	$199.29	4.468%	$208.1943	$208.19	$208.20	$208.20
Purchase #2	$121.59	4.770%	$127.3898	$127.39	$127.40	$127.40
Purchase #3	$78.45	5.585%	$82.8314	$82.83	$82.85	$82.80
Purchase #4	$140.96	13.648%	$160.1982	$160.20	$160.20	$160.20
Purchase #5	$105.68	6.428%	$112.4731	$112.47	$112.45	$112.50
Purchase #6	$78.42	4.560%	$81.996	$82.00	$82.00	$82.00
Purchase #7	$152.46	10.282%	$168.1359	$168.14	$168.15	$168.10
7 purchase totals =	$876.85		$941.2187	$941.22	$941.25	$941.20