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	$62.81	13.768%	$71.4577	$71.46	$71.45	$71.50
Purchase #2	$104.76	4.143%	$109.1002	$109.10	$109.10	$109.10
Purchase #3	$87.33	13.384%	$99.0182	$99.02	$99.00	$99.00
Purchase #4	$195.61	11.449%	$218.0054	$218.01	$218.00	$218.00
Purchase #5	$243.54	6.762%	$260.0082	$260.01	$260.00	$260.00
Purchase #6	$82.29	13.227%	$93.1745	$93.17	$93.15	$93.20
Purchase #7	$206.47	10.674%	$228.5086	$228.51	$228.50	$228.50
7 purchase totals =	$982.81		$1,079.2728	$1,079.28	$1,079.20	$1,079.30