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	$102.58	8.330%	$111.1249	$111.12	$111.10	$111.10
Purchase #2	$109.50	12.535%	$123.2258	$123.23	$123.25	$123.20
Purchase #3	$197.56	13.535%	$224.2997	$224.30	$224.30	$224.30
Purchase #4	$148.83	9.136%	$162.4271	$162.43	$162.45	$162.40
Purchase #5	$13.54	6.258%	$14.3873	$14.39	$14.40	$14.40
Purchase #6	$210.40	7.210%	$225.5698	$225.57	$225.55	$225.60
Purchase #7	$225.27	10.724%	$249.428	$249.43	$249.45	$249.40
7 purchase totals =	$1,007.68		$1,110.4626	$1,110.47	$1,110.50	$1,110.40