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	$220.77	11.265%	$245.6397	$245.64	$245.65	$245.60
Purchase #2	$20.70	3.189%	$21.3601	$21.36	$21.35	$21.40
Purchase #3	$130.44	4.606%	$136.4481	$136.45	$136.45	$136.40
Purchase #4	$151.93	13.562%	$172.5347	$172.53	$172.55	$172.50
Purchase #5	$229.69	12.581%	$258.5873	$258.59	$258.60	$258.60
Purchase #6	$156.83	8.751%	$170.5542	$170.55	$170.55	$170.60
Purchase #7	$61.96	8.503%	$67.2285	$67.23	$67.25	$67.20
7 purchase totals =	$972.32		$1,072.3526	$1,072.35	$1,072.40	$1,072.30