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	$210.38	6.446%	$223.9411	$223.94	$223.95	$223.90
Purchase #2	$73.88	11.785%	$82.5868	$82.59	$82.60	$82.60
Purchase #3	$177.74	4.449%	$185.6477	$185.65	$185.65	$185.60
Purchase #4	$111.89	5.325%	$117.8481	$117.85	$117.85	$117.80
Purchase #5	$42.93	12.199%	$48.167	$48.17	$48.15	$48.20
Purchase #6	$101.44	10.646%	$112.2393	$112.24	$112.25	$112.20
Purchase #7	$208.69	4.240%	$217.5385	$217.54	$217.55	$217.50
7 purchase totals =	$926.95		$987.9685	$987.98	$988.00	$987.80