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	$220.57	11.323%	$245.5451	$245.55	$245.55	$245.50
Purchase #2	$82.48	8.847%	$89.777	$89.78	$89.80	$89.80
Purchase #3	$50.77	8.229%	$54.9479	$54.95	$54.95	$54.90
Purchase #4	$173.32	13.820%	$197.2728	$197.27	$197.25	$197.30
Purchase #5	$6.56	8.832%	$7.1394	$7.14	$7.15	$7.10
Purchase #6	$82.40	3.628%	$85.3895	$85.39	$85.40	$85.40
Purchase #7	$119.35	11.225%	$132.747	$132.75	$132.75	$132.70
7 purchase totals =	$735.45		$812.8187	$812.83	$812.85	$812.70