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	$205.50	7.480%	$220.8714	$220.87	$220.85	$220.90
Purchase #2	$209.60	8.714%	$227.8645	$227.86	$227.85	$227.90
Purchase #3	$62.71	5.614%	$66.2305	$66.23	$66.25	$66.20
Purchase #4	$73.50	13.320%	$83.2902	$83.29	$83.30	$83.30
Purchase #5	$56.86	12.845%	$64.1637	$64.16	$64.15	$64.20
Purchase #6	$247.96	7.322%	$266.1156	$266.12	$266.10	$266.10
Purchase #7	$85.30	4.494%	$89.1334	$89.13	$89.15	$89.10
7 purchase totals =	$941.43		$1,017.6693	$1,017.66	$1,017.65	$1,017.70