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	$42.61	3.616%	$44.1508	$44.15	$44.15	$44.20
Purchase #2	$35.55	13.215%	$40.2479	$40.25	$40.25	$40.20
Purchase #3	$84.50	6.713%	$90.1725	$90.17	$90.15	$90.20
Purchase #4	$78.32	9.319%	$85.6186	$85.62	$85.60	$85.60
Purchase #5	$41.98	5.183%	$44.1558	$44.16	$44.15	$44.20
Purchase #6	$225.89	5.594%	$238.5263	$238.53	$238.55	$238.50
Purchase #7	$55.36	5.771%	$58.5548	$58.55	$58.55	$58.60
7 purchase totals =	$564.21		$601.4267	$601.43	$601.40	$601.50