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	$41.69	4.550%	$43.5869	$43.59	$43.60	$43.60
Purchase #2	$95.47	4.109%	$99.3929	$99.39	$99.40	$99.40
Purchase #3	$192.42	11.124%	$213.8248	$213.82	$213.80	$213.80
Purchase #4	$154.82	9.342%	$169.2833	$169.28	$169.30	$169.30
Purchase #5	$107.75	10.458%	$119.0185	$119.02	$119.00	$119.00
Purchase #6	$82.26	13.789%	$93.6028	$93.60	$93.60	$93.60
Purchase #7	$242.99	5.250%	$255.747	$255.75	$255.75	$255.70
7 purchase totals =	$917.40		$994.4562	$994.45	$994.45	$994.40