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	$186.72	8.860%	$203.2634	$203.26	$203.25	$203.30
Purchase #2	$160.47	9.184%	$175.2076	$175.21	$175.20	$175.20
Purchase #3	$162.44	3.785%	$168.5884	$168.59	$168.60	$168.60
Purchase #4	$43.39	7.788%	$46.7692	$46.77	$46.75	$46.80
Purchase #5	$52.89	13.251%	$59.8985	$59.90	$59.90	$59.90
Purchase #6	$131.51	8.692%	$142.9408	$142.94	$142.95	$142.90
Purchase #7	$87.48	8.344%	$94.7793	$94.78	$94.80	$94.80
7 purchase totals =	$824.90		$891.4472	$891.45	$891.45	$891.50