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	$194.78	13.518%	$221.1104	$221.11	$221.10	$221.10
Purchase #2	$146.98	10.507%	$162.4232	$162.42	$162.40	$162.40
Purchase #3	$184.49	6.479%	$196.4431	$196.44	$196.45	$196.40
Purchase #4	$76.55	11.685%	$85.4949	$85.49	$85.50	$85.50
Purchase #5	$184.93	3.324%	$191.0771	$191.08	$191.10	$191.10
Purchase #6	$113.26	3.378%	$117.0859	$117.09	$117.10	$117.10
Purchase #7	$139.88	10.233%	$154.1939	$154.19	$154.20	$154.20
7 purchase totals =	$1,040.87		$1,127.8285	$1,127.82	$1,127.85	$1,127.80