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	$33.57	11.874%	$37.5561	$37.56	$37.55	$37.60
Purchase #2	$219.26	7.798%	$236.3579	$236.36	$236.35	$236.40
Purchase #3	$172.67	10.485%	$190.7744	$190.77	$190.75	$190.80
Purchase #4	$49.90	8.840%	$54.3112	$54.31	$54.30	$54.30
Purchase #5	$199.76	6.793%	$213.3297	$213.33	$213.35	$213.30
Purchase #6	$38.38	13.633%	$43.6123	$43.61	$43.60	$43.60
Purchase #7	$188.69	12.265%	$211.8328	$211.83	$211.85	$211.80
7 purchase totals =	$902.23		$987.7744	$987.77	$987.75	$987.80