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	$118.93	8.166%	$128.6418	$128.64	$128.65	$128.60
Purchase #2	$92.29	11.268%	$102.6892	$102.69	$102.70	$102.70
Purchase #3	$103.50	8.672%	$112.4755	$112.48	$112.50	$112.50
Purchase #4	$168.32	12.171%	$188.8062	$188.81	$188.80	$188.80
Purchase #5	$89.40	12.836%	$100.8754	$100.88	$100.90	$100.90
Purchase #6	$197.48	4.766%	$206.8919	$206.89	$206.90	$206.90
Purchase #7	$58.34	11.740%	$65.1891	$65.19	$65.20	$65.20
7 purchase totals =	$828.26		$905.5691	$905.58	$905.65	$905.60