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	$67.66	5.749%	$71.5498	$71.55	$71.55	$71.50
Purchase #2	$216.96	11.509%	$241.9299	$241.93	$241.95	$241.90
Purchase #3	$56.37	5.379%	$59.4021	$59.40	$59.40	$59.40
Purchase #4	$100.40	11.768%	$112.2151	$112.22	$112.20	$112.20
Purchase #5	$90.70	3.247%	$93.645	$93.65	$93.65	$93.60
Purchase #6	$242.72	8.570%	$263.5211	$263.52	$263.50	$263.50
Purchase #7	$106.52	3.764%	$110.5294	$110.53	$110.55	$110.50
7 purchase totals =	$881.33		$952.7924	$952.80	$952.80	$952.60