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	$203.45	9.166%	$222.0982	$222.10	$222.10	$222.10
Purchase #2	$192.61	12.855%	$217.37	$217.37	$217.35	$217.40
Purchase #3	$122.55	11.270%	$136.3614	$136.36	$136.35	$136.40
Purchase #4	$200.68	7.360%	$215.45	$215.45	$215.45	$215.50
Purchase #5	$94.49	4.167%	$98.4274	$98.43	$98.45	$98.40
Purchase #6	$209.55	4.110%	$218.1625	$218.16	$218.15	$218.20
Purchase #7	$100.65	4.721%	$105.4017	$105.40	$105.40	$105.40
7 purchase totals =	$1,123.98		$1,213.2712	$1,213.27	$1,213.25	$1,213.40