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	$186.96	6.552%	$199.2096	$199.21	$199.20	$199.20
Purchase #2	$47.35	6.737%	$50.54	$50.54	$50.55	$50.50
Purchase #3	$99.80	12.355%	$112.1303	$112.13	$112.15	$112.10
Purchase #4	$57.51	4.109%	$59.8731	$59.87	$59.85	$59.90
Purchase #5	$63.46	13.144%	$71.8012	$71.80	$71.80	$71.80
Purchase #6	$231.67	12.454%	$260.5222	$260.52	$260.50	$260.50
Purchase #7	$61.57	10.464%	$68.0127	$68.01	$68.00	$68.00
7 purchase totals =	$748.32		$822.0891	$822.08	$822.05	$822.00