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	$37.45	11.486%	$41.7515	$41.75	$41.75	$41.80
Purchase #2	$143.74	3.521%	$148.8011	$148.80	$148.80	$148.80
Purchase #3	$146.39	9.161%	$159.8008	$159.80	$159.80	$159.80
Purchase #4	$210.78	7.858%	$227.3431	$227.34	$227.35	$227.30
Purchase #5	$206.41	4.312%	$215.3104	$215.31	$215.30	$215.30
Purchase #6	$59.90	12.543%	$67.4133	$67.41	$67.40	$67.40
Purchase #7	$246.59	6.603%	$262.8723	$262.87	$262.85	$262.90
7 purchase totals =	$1,051.26		$1,123.2925	$1,123.28	$1,123.25	$1,123.30