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	$173.44	8.577%	$188.3159	$188.32	$188.30	$188.30
Purchase #2	$221.54	12.109%	$248.3663	$248.37	$248.35	$248.40
Purchase #3	$20.50	4.146%	$21.3499	$21.35	$21.35	$21.30
Purchase #4	$92.36	11.257%	$102.757	$102.76	$102.75	$102.80
Purchase #5	$186.39	3.679%	$193.2473	$193.25	$193.25	$193.20
Purchase #6	$158.57	6.480%	$168.8453	$168.85	$168.85	$168.80
Purchase #7	$90.27	4.210%	$94.0704	$94.07	$94.05	$94.10
7 purchase totals =	$943.07		$1,016.9521	$1,016.97	$1,016.90	$1,016.90