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	$51.50	3.362%	$53.2314	$53.23	$53.25	$53.20
Purchase #2	$12.84	13.166%	$14.5305	$14.53	$14.55	$14.50
Purchase #3	$75.52	8.821%	$82.1816	$82.18	$82.20	$82.20
Purchase #4	$27.63	12.523%	$31.0901	$31.09	$31.10	$31.10
Purchase #5	$43.41	10.774%	$48.087	$48.09	$48.10	$48.10
Purchase #6	$94.71	3.282%	$97.8184	$97.82	$97.80	$97.80
Purchase #7	$113.99	12.197%	$127.8934	$127.89	$127.90	$127.90
7 purchase totals =	$419.60		$454.8324	$454.83	$454.90	$454.80