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	$59.94	5.845%	$63.4435	$63.44	$63.45	$63.40
Purchase #2	$72.62	8.635%	$78.8907	$78.89	$78.90	$78.90
Purchase #3	$231.54	4.243%	$241.3642	$241.36	$241.35	$241.40
Purchase #4	$106.80	12.220%	$119.851	$119.85	$119.85	$119.90
Purchase #5	$133.77	5.770%	$141.4885	$141.49	$141.50	$141.50
Purchase #6	$242.44	6.701%	$258.6859	$258.69	$258.70	$258.70
Purchase #7	$198.74	12.244%	$223.0737	$223.07	$223.05	$223.10
7 purchase totals =	$1,045.85		$1,126.7975	$1,126.79	$1,126.80	$1,126.90