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	$44.61	4.207%	$46.4867	$46.49	$46.50	$46.50
Purchase #2	$11.87	11.443%	$13.2283	$13.23	$13.25	$13.20
Purchase #3	$223.90	6.533%	$238.5274	$238.53	$238.55	$238.50
Purchase #4	$197.69	12.845%	$223.0833	$223.08	$223.10	$223.10
Purchase #5	$60.56	6.744%	$64.6442	$64.64	$64.65	$64.60
Purchase #6	$150.51	5.320%	$158.5171	$158.52	$158.50	$158.50
Purchase #7	$146.84	9.265%	$160.4447	$160.44	$160.45	$160.40
7 purchase totals =	$835.98		$904.9317	$904.93	$905.00	$904.80