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	$133.82	9.150%	$146.0645	$146.06	$146.05	$146.10
Purchase #2	$114.56	9.350%	$125.2714	$125.27	$125.25	$125.30
Purchase #3	$97.46	10.317%	$107.5149	$107.51	$107.50	$107.50
Purchase #4	$209.83	11.357%	$233.6604	$233.66	$233.65	$233.70
Purchase #5	$39.99	7.274%	$42.8989	$42.90	$42.90	$42.90
Purchase #6	$132.53	3.427%	$137.0718	$137.07	$137.05	$137.10
Purchase #7	$83.44	7.348%	$89.5712	$89.57	$89.55	$89.60
7 purchase totals =	$811.63		$882.0531	$882.04	$881.95	$882.20