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	$243.98	6.547%	$259.9534	$259.95	$259.95	$260.00
Purchase #2	$15.59	11.528%	$17.3872	$17.39	$17.40	$17.40
Purchase #3	$227.84	6.447%	$242.5288	$242.53	$242.55	$242.50
Purchase #4	$30.90	6.479%	$32.902	$32.90	$32.90	$32.90
Purchase #5	$179.44	6.111%	$190.4056	$190.41	$190.40	$190.40
Purchase #6	$75.54	10.370%	$83.3735	$83.37	$83.35	$83.40
Purchase #7	$210.34	5.573%	$222.0622	$222.06	$222.05	$222.10
7 purchase totals =	$983.63		$1,048.6127	$1,048.61	$1,048.60	$1,048.70