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	$73.43	11.582%	$81.9347	$81.93	$81.95	$81.90
Purchase #2	$166.47	10.476%	$183.9094	$183.91	$183.90	$183.90
Purchase #3	$50.53	13.707%	$57.4561	$57.46	$57.45	$57.50
Purchase #4	$103.92	3.430%	$107.4845	$107.48	$107.50	$107.50
Purchase #5	$179.68	11.740%	$200.7744	$200.77	$200.75	$200.80
Purchase #6	$56.78	5.504%	$59.9052	$59.91	$59.90	$59.90
Purchase #7	$12.58	7.343%	$13.5037	$13.50	$13.50	$13.50
7 purchase totals =	$643.39		$704.9680	$704.96	$704.95	$705.00