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	$168.61	8.444%	$182.8474	$182.85	$182.85	$182.80
Purchase #2	$112.67	7.154%	$120.7304	$120.73	$120.75	$120.70
Purchase #3	$17.85	3.691%	$18.5088	$18.51	$18.50	$18.50
Purchase #4	$202.92	6.559%	$216.2295	$216.23	$216.25	$216.20
Purchase #5	$94.30	6.568%	$100.4936	$100.49	$100.50	$100.50
Purchase #6	$127.60	4.578%	$133.4415	$133.44	$133.45	$133.40
Purchase #7	$220.72	11.400%	$245.8821	$245.88	$245.90	$245.90
7 purchase totals =	$944.67		$1,018.1333	$1,018.13	$1,018.20	$1,018.00