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	$82.77	3.569%	$85.7241	$85.72	$85.70	$85.70
Purchase #2	$99.49	12.183%	$111.6109	$111.61	$111.60	$111.60
Purchase #3	$169.84	7.181%	$182.0362	$182.04	$182.05	$182.00
Purchase #4	$123.75	8.402%	$134.1475	$134.15	$134.15	$134.10
Purchase #5	$107.30	4.847%	$112.5008	$112.50	$112.50	$112.50
Purchase #6	$85.56	4.177%	$89.1338	$89.13	$89.15	$89.10
Purchase #7	$65.70	5.622%	$69.3937	$69.39	$69.40	$69.40
7 purchase totals =	$734.41		$784.5470	$784.54	$784.55	$784.40