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	$69.33	5.156%	$72.9047	$72.90	$72.90	$72.90
Purchase #2	$218.43	5.779%	$231.0531	$231.05	$231.05	$231.10
Purchase #3	$23.83	10.494%	$26.3307	$26.33	$26.35	$26.30
Purchase #4	$66.80	8.629%	$72.5642	$72.56	$72.55	$72.60
Purchase #5	$222.60	10.484%	$245.9374	$245.94	$245.95	$245.90
Purchase #6	$90.90	10.842%	$100.7554	$100.76	$100.75	$100.80
Purchase #7	$164.47	5.671%	$173.7971	$173.80	$173.80	$173.80
7 purchase totals =	$856.36		$923.3426	$923.34	$923.35	$923.40