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	$85.69	8.166%	$92.6874	$92.69	$92.70	$92.70
Purchase #2	$50.80	5.472%	$53.5798	$53.58	$53.60	$53.60
Purchase #3	$231.61	12.243%	$259.966	$259.97	$259.95	$260.00
Purchase #4	$89.96	4.374%	$93.8949	$93.89	$93.90	$93.90
Purchase #5	$159.44	7.325%	$171.119	$171.12	$171.10	$171.10
Purchase #6	$140.75	6.671%	$150.1394	$150.14	$150.15	$150.10
Purchase #7	$183.78	6.528%	$195.7772	$195.78	$195.80	$195.80
7 purchase totals =	$942.03		$1,017.1637	$1,017.17	$1,017.20	$1,017.20