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	$94.80	10.822%	$105.0593	$105.06	$105.05	$105.10
Purchase #2	$30.29	11.522%	$33.78	$33.78	$33.80	$33.80
Purchase #3	$75.41	13.334%	$85.4652	$85.47	$85.45	$85.50
Purchase #4	$155.37	9.360%	$169.9126	$169.91	$169.90	$169.90
Purchase #5	$140.42	11.384%	$156.4054	$156.41	$156.40	$156.40
Purchase #6	$12.58	5.584%	$13.2825	$13.28	$13.30	$13.30
Purchase #7	$215.90	4.696%	$226.0387	$226.04	$226.05	$226.00
7 purchase totals =	$724.77		$789.9437	$789.95	$789.95	$790.00