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	$61.81	5.801%	$65.3956	$65.40	$65.40	$65.40
Purchase #2	$55.74	9.834%	$61.2215	$61.22	$61.20	$61.20
Purchase #3	$67.47	7.307%	$72.4	$72.40	$72.40	$72.40
Purchase #4	$201.71	6.650%	$215.1237	$215.12	$215.10	$215.10
Purchase #5	$128.73	13.431%	$146.0197	$146.02	$146.00	$146.00
Purchase #6	$32.88	11.389%	$36.6247	$36.62	$36.60	$36.60
Purchase #7	$113.66	11.453%	$126.6775	$126.68	$126.70	$126.70
7 purchase totals =	$662.00		$723.4627	$723.46	$723.40	$723.40