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	$191.55	6.858%	$204.6865	$204.69	$204.70	$204.70
Purchase #2	$130.31	7.301%	$139.8239	$139.82	$139.80	$139.80
Purchase #3	$218.31	7.815%	$235.3709	$235.37	$235.35	$235.40
Purchase #4	$206.56	9.328%	$225.8279	$225.83	$225.85	$225.80
Purchase #5	$246.96	11.156%	$274.5109	$274.51	$274.50	$274.50
Purchase #6	$138.68	3.658%	$143.7529	$143.75	$143.75	$143.80
Purchase #7	$106.54	4.684%	$111.5303	$111.53	$111.55	$111.50
7 purchase totals =	$1,238.91		$1,335.5033	$1,335.50	$1,335.50	$1,335.50