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	$64.43	7.610%	$69.3331	$69.33	$69.35	$69.30
Purchase #2	$109.78	12.337%	$123.3236	$123.32	$123.30	$123.30
Purchase #3	$111.53	10.180%	$122.8838	$122.88	$122.90	$122.90
Purchase #4	$125.94	11.572%	$140.5138	$140.51	$140.50	$140.50
Purchase #5	$209.43	6.406%	$222.8461	$222.85	$222.85	$222.80
Purchase #6	$158.27	7.675%	$170.4172	$170.42	$170.40	$170.40
Purchase #7	$183.40	13.414%	$208.0013	$208.00	$208.00	$208.00
7 purchase totals =	$962.78		$1,057.3189	$1,057.31	$1,057.30	$1,057.20