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	$7.81	12.696%	$8.8016	$8.80	$8.80	$8.80
Purchase #2	$158.90	5.148%	$167.0802	$167.08	$167.10	$167.10
Purchase #3	$185.92	10.532%	$205.5011	$205.50	$205.50	$205.50
Purchase #4	$33.60	7.360%	$36.073	$36.07	$36.05	$36.10
Purchase #5	$108.70	13.662%	$123.5506	$123.55	$123.55	$123.60
Purchase #6	$236.81	8.454%	$256.8299	$256.83	$256.85	$256.80
Purchase #7	$85.95	4.108%	$89.4808	$89.48	$89.50	$89.50
7 purchase totals =	$817.69		$887.3172	$887.31	$887.35	$887.40