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	$182.54	13.157%	$206.5568	$206.56	$206.55	$206.60
Purchase #2	$74.67	5.281%	$78.6133	$78.61	$78.60	$78.60
Purchase #3	$186.71	5.390%	$196.7737	$196.77	$196.75	$196.80
Purchase #4	$59.34	9.337%	$64.8806	$64.88	$64.90	$64.90
Purchase #5	$114.33	6.670%	$121.9558	$121.96	$121.95	$122.00
Purchase #6	$186.81	8.822%	$203.2904	$203.29	$203.30	$203.30
Purchase #7	$248.30	4.290%	$258.9521	$258.95	$258.95	$259.00
7 purchase totals =	$1,052.70		$1,131.0227	$1,131.02	$1,131.00	$1,131.20