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	$23.35	4.241%	$24.3403	$24.34	$24.35	$24.30
Purchase #2	$158.45	13.136%	$179.264	$179.26	$179.25	$179.30
Purchase #3	$238.91	10.444%	$263.8618	$263.86	$263.85	$263.90
Purchase #4	$94.66	5.469%	$99.837	$99.84	$99.85	$99.80
Purchase #5	$36.77	3.146%	$37.9268	$37.93	$37.95	$37.90
Purchase #6	$206.76	8.409%	$224.1464	$224.15	$224.15	$224.10
Purchase #7	$217.63	7.308%	$233.5344	$233.53	$233.55	$233.50
7 purchase totals =	$976.53		$1,062.9107	$1,062.91	$1,062.95	$1,062.80