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	$125.66	7.313%	$134.8495	$134.85	$134.85	$134.80
Purchase #2	$82.77	9.667%	$90.7714	$90.77	$90.75	$90.80
Purchase #3	$206.72	5.828%	$218.7676	$218.77	$218.75	$218.80
Purchase #4	$37.87	6.392%	$40.2907	$40.29	$40.30	$40.30
Purchase #5	$50.95	4.572%	$53.2794	$53.28	$53.30	$53.30
Purchase #6	$203.47	13.672%	$231.2884	$231.29	$231.30	$231.30
Purchase #7	$229.48	4.588%	$240.0085	$240.01	$240.00	$240.00
7 purchase totals =	$936.92		$1,009.2555	$1,009.26	$1,009.25	$1,009.30