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	$36.27	6.103%	$38.4836	$38.48	$38.50	$38.50
Purchase #2	$9.92	6.380%	$10.5529	$10.55	$10.55	$10.60
Purchase #3	$39.97	6.616%	$42.6144	$42.61	$42.60	$42.60
Purchase #4	$53.75	13.663%	$61.0939	$61.09	$61.10	$61.10
Purchase #5	$121.71	9.193%	$132.8988	$132.90	$132.90	$132.90
Purchase #6	$216.27	10.458%	$238.8875	$238.89	$238.90	$238.90
Purchase #7	$167.86	7.777%	$180.9145	$180.91	$180.90	$180.90
7 purchase totals =	$645.75		$705.4456	$705.43	$705.45	$705.50