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	$237.97	10.467%	$262.8783	$262.88	$262.90	$262.90
Purchase #2	$80.78	5.648%	$85.3425	$85.34	$85.35	$85.30
Purchase #3	$93.58	7.854%	$100.9298	$100.93	$100.95	$100.90
Purchase #4	$145.66	5.616%	$153.8403	$153.84	$153.85	$153.80
Purchase #5	$227.96	4.331%	$237.8329	$237.83	$237.85	$237.80
Purchase #6	$35.56	13.140%	$40.2326	$40.23	$40.25	$40.20
Purchase #7	$164.74	11.198%	$183.1876	$183.19	$183.20	$183.20
7 purchase totals =	$986.25		$1,064.2440	$1,064.24	$1,064.35	$1,064.10