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	$7.42	5.484%	$7.8269	$7.83	$7.85	$7.80
Purchase #2	$52.33	5.611%	$55.2662	$55.27	$55.25	$55.30
Purchase #3	$207.93	5.735%	$219.8548	$219.85	$219.85	$219.90
Purchase #4	$17.73	4.514%	$18.5303	$18.53	$18.55	$18.50
Purchase #5	$115.31	7.675%	$124.16	$124.16	$124.15	$124.20
Purchase #6	$90.70	9.820%	$99.6067	$99.61	$99.60	$99.60
Purchase #7	$169.60	12.402%	$190.6338	$190.63	$190.65	$190.60
7 purchase totals =	$661.02		$715.8787	$715.88	$715.90	$715.90