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	$205.50	13.638%	$233.5261	$233.53	$233.55	$233.50
Purchase #2	$56.77	7.786%	$61.1901	$61.19	$61.20	$61.20
Purchase #3	$207.57	7.710%	$223.5736	$223.57	$223.55	$223.60
Purchase #4	$138.45	11.127%	$153.8553	$153.86	$153.85	$153.90
Purchase #5	$201.61	10.151%	$222.0754	$222.08	$222.10	$222.10
Purchase #6	$59.38	8.670%	$64.5282	$64.53	$64.55	$64.50
Purchase #7	$238.87	7.356%	$256.4413	$256.44	$256.45	$256.40
7 purchase totals =	$1,108.15		$1,215.1900	$1,215.20	$1,215.25	$1,215.20