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	$62.61	7.337%	$67.2037	$67.20	$67.20	$67.20
Purchase #2	$199.68	11.451%	$222.5454	$222.55	$222.55	$222.50
Purchase #3	$58.37	13.799%	$66.4245	$66.42	$66.40	$66.40
Purchase #4	$79.64	11.210%	$88.5676	$88.57	$88.55	$88.60
Purchase #5	$182.61	7.718%	$196.7038	$196.70	$196.70	$196.70
Purchase #6	$172.77	5.236%	$181.8162	$181.82	$181.80	$181.80
Purchase #7	$53.58	7.408%	$57.5492	$57.55	$57.55	$57.50
7 purchase totals =	$809.26		$880.8104	$880.81	$880.75	$880.70