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	$133.52	3.776%	$138.5617	$138.56	$138.55	$138.60
Purchase #2	$237.76	7.228%	$254.9453	$254.95	$254.95	$254.90
Purchase #3	$123.43	7.700%	$132.9341	$132.93	$132.95	$132.90
Purchase #4	$142.41	6.712%	$151.9686	$151.97	$151.95	$152.00
Purchase #5	$115.31	11.779%	$128.8924	$128.89	$128.90	$128.90
Purchase #6	$168.80	6.761%	$180.2126	$180.21	$180.20	$180.20
Purchase #7	$137.59	10.802%	$152.4525	$152.45	$152.45	$152.50
7 purchase totals =	$1,058.82		$1,139.9672	$1,139.96	$1,139.95	$1,140.00