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	$104.30	5.210%	$109.734	$109.73	$109.75	$109.70
Purchase #2	$54.49	4.468%	$56.9246	$56.92	$56.90	$56.90
Purchase #3	$98.71	5.871%	$104.5053	$104.51	$104.50	$104.50
Purchase #4	$75.49	10.449%	$83.378	$83.38	$83.40	$83.40
Purchase #5	$108.26	7.508%	$116.3882	$116.39	$116.40	$116.40
Purchase #6	$181.35	10.366%	$200.1487	$200.15	$200.15	$200.10
Purchase #7	$234.28	5.266%	$246.6172	$246.62	$246.60	$246.60
7 purchase totals =	$856.88		$917.6960	$917.70	$917.70	$917.60