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	$134.31	11.243%	$149.4105	$149.41	$149.40	$149.40
Purchase #2	$157.45	6.425%	$167.5662	$167.57	$167.55	$167.60
Purchase #3	$232.81	12.460%	$261.8181	$261.82	$261.80	$261.80
Purchase #4	$82.81	3.696%	$85.8707	$85.87	$85.85	$85.90
Purchase #5	$163.25	13.308%	$184.9753	$184.98	$185.00	$185.00
Purchase #6	$132.72	11.455%	$147.9231	$147.92	$147.90	$147.90
Purchase #7	$162.54	10.115%	$178.9809	$178.98	$179.00	$179.00
7 purchase totals =	$1,065.89		$1,176.5448	$1,176.55	$1,176.50	$1,176.60