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	$207.83	4.197%	$216.5526	$216.55	$216.55	$216.60
Purchase #2	$121.62	5.579%	$128.4052	$128.41	$128.40	$128.40
Purchase #3	$208.26	3.442%	$215.4283	$215.43	$215.45	$215.40
Purchase #4	$96.77	13.400%	$109.7372	$109.74	$109.75	$109.70
Purchase #5	$51.60	5.317%	$54.3436	$54.34	$54.35	$54.30
Purchase #6	$134.40	6.855%	$143.6131	$143.61	$143.60	$143.60
Purchase #7	$101.93	11.129%	$113.2738	$113.27	$113.25	$113.30
7 purchase totals =	$922.41		$981.3538	$981.35	$981.35	$981.30