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	$126.89	9.575%	$139.0397	$139.04	$139.05	$139.00
Purchase #2	$213.56	4.424%	$223.0079	$223.01	$223.00	$223.00
Purchase #3	$11.32	6.564%	$12.063	$12.06	$12.05	$12.10
Purchase #4	$30.82	10.107%	$33.935	$33.94	$33.95	$33.90
Purchase #5	$84.72	10.371%	$93.5063	$93.51	$93.50	$93.50
Purchase #6	$94.32	10.460%	$104.1859	$104.19	$104.20	$104.20
Purchase #7	$138.85	3.763%	$144.0749	$144.07	$144.05	$144.10
7 purchase totals =	$700.48		$749.8127	$749.82	$749.80	$749.80