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	$213.86	6.337%	$227.4123	$227.41	$227.40	$227.40
Purchase #2	$60.81	10.656%	$67.2899	$67.29	$67.30	$67.30
Purchase #3	$97.95	12.158%	$109.8588	$109.86	$109.85	$109.90
Purchase #4	$93.46	13.168%	$105.7668	$105.77	$105.75	$105.80
Purchase #5	$227.41	9.761%	$249.6075	$249.61	$249.60	$249.60
Purchase #6	$215.87	13.861%	$245.7917	$245.79	$245.80	$245.80
Purchase #7	$199.40	9.304%	$217.9522	$217.95	$217.95	$218.00
7 purchase totals =	$1,108.76		$1,223.6792	$1,223.68	$1,223.65	$1,223.80