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	$113.66	10.426%	$125.5102	$125.51	$125.50	$125.50
Purchase #2	$54.50	9.337%	$59.5887	$59.59	$59.60	$59.60
Purchase #3	$138.43	3.598%	$143.4107	$143.41	$143.40	$143.40
Purchase #4	$183.61	6.166%	$194.9314	$194.93	$194.95	$194.90
Purchase #5	$86.25	4.299%	$89.9579	$89.96	$89.95	$90.00
Purchase #6	$114.99	10.618%	$127.1996	$127.20	$127.20	$127.20
Purchase #7	$16.51	8.319%	$17.8835	$17.88	$17.90	$17.90
7 purchase totals =	$707.95		$758.4820	$758.48	$758.50	$758.50