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	$97.66	4.551%	$102.1045	$102.10	$102.10	$102.10
Purchase #2	$119.45	3.194%	$123.2652	$123.27	$123.25	$123.30
Purchase #3	$82.46	3.526%	$85.3675	$85.37	$85.35	$85.40
Purchase #4	$27.91	11.115%	$31.0122	$31.01	$31.00	$31.00
Purchase #5	$65.95	10.418%	$72.8207	$72.82	$72.80	$72.80
Purchase #6	$89.57	6.395%	$95.298	$95.30	$95.30	$95.30
Purchase #7	$200.54	9.606%	$219.8039	$219.80	$219.80	$219.80
7 purchase totals =	$683.54		$729.6720	$729.67	$729.60	$729.70