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	$135.38	12.617%	$152.4609	$152.46	$152.45	$152.50
Purchase #2	$80.51	11.835%	$90.0384	$90.04	$90.05	$90.00
Purchase #3	$146.79	3.564%	$152.0216	$152.02	$152.00	$152.00
Purchase #4	$206.39	13.660%	$234.5829	$234.58	$234.60	$234.60
Purchase #5	$93.67	9.119%	$102.2118	$102.21	$102.20	$102.20
Purchase #6	$17.63	3.657%	$18.2747	$18.27	$18.25	$18.30
Purchase #7	$239.55	5.645%	$253.0726	$253.07	$253.05	$253.10
7 purchase totals =	$919.92		$1,002.6629	$1,002.65	$1,002.60	$1,002.70