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	$94.78	4.849%	$99.3759	$99.38	$99.40	$99.40
Purchase #2	$29.48	11.535%	$32.8805	$32.88	$32.90	$32.90
Purchase #3	$212.31	6.448%	$225.9997	$226.00	$226.00	$226.00
Purchase #4	$202.71	10.203%	$223.3925	$223.39	$223.40	$223.40
Purchase #5	$90.59	12.207%	$101.6483	$101.65	$101.65	$101.60
Purchase #6	$42.30	8.139%	$45.7428	$45.74	$45.75	$45.70
Purchase #7	$132.96	8.724%	$144.5594	$144.56	$144.55	$144.60
7 purchase totals =	$805.13		$873.5991	$873.60	$873.65	$873.60