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	$89.25	12.332%	$100.2563	$100.26	$100.25	$100.30
Purchase #2	$7.90	7.119%	$8.4624	$8.46	$8.45	$8.50
Purchase #3	$121.29	10.383%	$133.8835	$133.88	$133.90	$133.90
Purchase #4	$44.71	8.120%	$48.3405	$48.34	$48.35	$48.30
Purchase #5	$244.35	3.545%	$253.0122	$253.01	$253.00	$253.00
Purchase #6	$104.52	9.120%	$114.0522	$114.05	$114.05	$114.10
Purchase #7	$87.99	13.524%	$99.8898	$99.89	$99.90	$99.90
7 purchase totals =	$700.01		$757.8969	$757.89	$757.90	$758.00