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	$56.44	8.293%	$61.1206	$61.12	$61.10	$61.10
Purchase #2	$66.29	6.354%	$70.5021	$70.50	$70.50	$70.50
Purchase #3	$31.81	13.665%	$36.1568	$36.16	$36.15	$36.20
Purchase #4	$80.37	3.120%	$82.8775	$82.88	$82.90	$82.90
Purchase #5	$227.60	4.253%	$237.2798	$237.28	$237.30	$237.30
Purchase #6	$247.84	10.334%	$273.4518	$273.45	$273.45	$273.50
Purchase #7	$193.78	13.225%	$219.4074	$219.41	$219.40	$219.40
7 purchase totals =	$904.13		$980.7960	$980.80	$980.80	$980.90