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	$63.57	6.454%	$67.6728	$67.67	$67.65	$67.70
Purchase #2	$45.53	13.638%	$51.7394	$51.74	$51.75	$51.70
Purchase #3	$216.81	5.814%	$229.4153	$229.42	$229.40	$229.40
Purchase #4	$37.98	6.698%	$40.5239	$40.52	$40.50	$40.50
Purchase #5	$64.39	4.408%	$67.2283	$67.23	$67.25	$67.20
Purchase #6	$153.54	9.531%	$168.1739	$168.17	$168.15	$168.20
Purchase #7	$116.52	6.791%	$124.4329	$124.43	$124.45	$124.40
7 purchase totals =	$698.34		$749.1865	$749.18	$749.15	$749.10