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	$85.97	4.236%	$89.6117	$89.61	$89.60	$89.60
Purchase #2	$91.56	12.502%	$103.0068	$103.01	$103.00	$103.00
Purchase #3	$91.67	8.439%	$99.406	$99.41	$99.40	$99.40
Purchase #4	$136.99	12.361%	$153.9233	$153.92	$153.90	$153.90
Purchase #5	$153.50	3.821%	$159.3652	$159.37	$159.35	$159.40
Purchase #6	$242.93	5.330%	$255.8782	$255.88	$255.90	$255.90
Purchase #7	$138.35	3.461%	$143.1383	$143.14	$143.15	$143.10
7 purchase totals =	$940.97		$1,004.3295	$1,004.34	$1,004.30	$1,004.30