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	$185.41	5.309%	$195.2534	$195.25	$195.25	$195.30
Purchase #2	$37.83	12.417%	$42.5274	$42.53	$42.55	$42.50
Purchase #3	$220.42	9.696%	$241.7919	$241.79	$241.80	$241.80
Purchase #4	$214.98	13.625%	$244.271	$244.27	$244.25	$244.30
Purchase #5	$37.79	6.248%	$40.1511	$40.15	$40.15	$40.20
Purchase #6	$100.46	12.197%	$112.7131	$112.71	$112.70	$112.70
Purchase #7	$190.47	9.478%	$208.5227	$208.52	$208.50	$208.50
7 purchase totals =	$987.36		$1,085.2306	$1,085.22	$1,085.20	$1,085.30