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	$130.37	10.369%	$143.8881	$143.89	$143.90	$143.90
Purchase #2	$231.98	9.872%	$254.8811	$254.88	$254.90	$254.90
Purchase #3	$154.52	8.700%	$167.9632	$167.96	$167.95	$168.00
Purchase #4	$84.49	4.852%	$88.5895	$88.59	$88.60	$88.60
Purchase #5	$111.34	12.281%	$125.0137	$125.01	$125.00	$125.00
Purchase #6	$179.59	8.266%	$194.4349	$194.43	$194.45	$194.40
Purchase #7	$88.50	4.697%	$92.6568	$92.66	$92.65	$92.70
7 purchase totals =	$980.79		$1,067.4273	$1,067.42	$1,067.45	$1,067.50