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	$222.68	6.115%	$236.2969	$236.30	$236.30	$236.30
Purchase #2	$214.32	6.662%	$228.598	$228.60	$228.60	$228.60
Purchase #3	$60.28	11.367%	$67.132	$67.13	$67.15	$67.10
Purchase #4	$38.32	5.181%	$40.3054	$40.31	$40.30	$40.30
Purchase #5	$18.37	3.180%	$18.9542	$18.95	$18.95	$19.00
Purchase #6	$84.47	8.731%	$91.8451	$91.85	$91.85	$91.80
Purchase #7	$238.38	10.104%	$262.4659	$262.47	$262.45	$262.50
7 purchase totals =	$876.82		$945.5975	$945.61	$945.60	$945.60