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	$91.48	11.859%	$102.3286	$102.33	$102.35	$102.30
Purchase #2	$20.56	13.789%	$23.395	$23.40	$23.40	$23.40
Purchase #3	$57.32	4.577%	$59.9435	$59.94	$59.95	$59.90
Purchase #4	$195.85	8.454%	$212.4072	$212.41	$212.40	$212.40
Purchase #5	$40.68	4.624%	$42.561	$42.56	$42.55	$42.60
Purchase #6	$158.93	10.545%	$175.6892	$175.69	$175.70	$175.70
Purchase #7	$192.55	13.170%	$217.9088	$217.91	$217.90	$217.90
7 purchase totals =	$757.37		$834.2333	$834.24	$834.25	$834.20