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	$66.54	3.404%	$68.805	$68.81	$68.80	$68.80
Purchase #2	$53.95	10.366%	$59.5425	$59.54	$59.55	$59.50
Purchase #3	$236.29	8.474%	$256.3132	$256.31	$256.30	$256.30
Purchase #4	$18.48	12.325%	$20.7577	$20.76	$20.75	$20.80
Purchase #5	$136.60	4.515%	$142.7675	$142.77	$142.75	$142.80
Purchase #6	$159.89	4.457%	$167.0163	$167.02	$167.00	$167.00
Purchase #7	$212.99	8.849%	$231.8375	$231.84	$231.85	$231.80
7 purchase totals =	$884.74		$947.0397	$947.05	$947.00	$947.00