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	$111.88	12.741%	$126.1346	$126.13	$126.15	$126.10
Purchase #2	$18.80	9.241%	$20.5373	$20.54	$20.55	$20.50
Purchase #3	$6.59	6.790%	$7.0375	$7.04	$7.05	$7.00
Purchase #4	$66.52	10.547%	$73.5359	$73.54	$73.55	$73.50
Purchase #5	$196.36	5.549%	$207.256	$207.26	$207.25	$207.30
Purchase #6	$135.94	4.254%	$141.7229	$141.72	$141.70	$141.70
Purchase #7	$108.61	13.755%	$123.5493	$123.55	$123.55	$123.50
7 purchase totals =	$644.70		$699.7735	$699.78	$699.80	$699.60