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	$203.95	12.326%	$229.0889	$229.09	$229.10	$229.10
Purchase #2	$38.43	11.239%	$42.7491	$42.75	$42.75	$42.70
Purchase #3	$38.61	12.669%	$43.5015	$43.50	$43.50	$43.50
Purchase #4	$20.83	12.458%	$23.425	$23.43	$23.45	$23.40
Purchase #5	$38.36	12.829%	$43.2812	$43.28	$43.30	$43.30
Purchase #6	$92.83	8.754%	$100.9563	$100.96	$100.95	$101.00
Purchase #7	$208.56	5.229%	$219.4656	$219.47	$219.45	$219.50
7 purchase totals =	$641.57		$702.4676	$702.48	$702.50	$702.50