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	$162.40	3.676%	$168.3698	$168.37	$168.35	$168.40
Purchase #2	$75.59	5.159%	$79.4897	$79.49	$79.50	$79.50
Purchase #3	$101.55	11.534%	$113.2628	$113.26	$113.25	$113.30
Purchase #4	$225.30	13.397%	$255.4834	$255.48	$255.50	$255.50
Purchase #5	$149.87	13.625%	$170.2898	$170.29	$170.30	$170.30
Purchase #6	$42.54	7.208%	$45.6063	$45.61	$45.60	$45.60
Purchase #7	$229.86	12.291%	$258.1121	$258.11	$258.10	$258.10
7 purchase totals =	$987.11		$1,090.6139	$1,090.61	$1,090.60	$1,090.70