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	$218.88	11.791%	$244.6881	$244.69	$244.70	$244.70
Purchase #2	$59.33	4.280%	$61.8693	$61.87	$61.85	$61.90
Purchase #3	$76.74	11.358%	$85.4561	$85.46	$85.45	$85.50
Purchase #4	$114.53	4.627%	$119.8293	$119.83	$119.85	$119.80
Purchase #5	$201.89	5.736%	$213.4704	$213.47	$213.45	$213.50
Purchase #6	$25.32	10.276%	$27.9219	$27.92	$27.90	$27.90
Purchase #7	$14.63	11.761%	$16.3506	$16.35	$16.35	$16.40
7 purchase totals =	$711.32		$769.5857	$769.59	$769.55	$769.70