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	$188.77	6.186%	$200.4473	$200.45	$200.45	$200.40
Purchase #2	$199.80	6.743%	$213.2725	$213.27	$213.25	$213.30
Purchase #3	$217.92	4.868%	$228.5283	$228.53	$228.55	$228.50
Purchase #4	$237.69	7.864%	$256.3819	$256.38	$256.40	$256.40
Purchase #5	$240.38	7.433%	$258.2474	$258.25	$258.25	$258.20
Purchase #6	$148.31	13.195%	$167.8795	$167.88	$167.90	$167.90
Purchase #7	$231.88	6.131%	$246.0966	$246.10	$246.10	$246.10
7 purchase totals =	$1,464.75		$1,570.8535	$1,570.86	$1,570.90	$1,570.80