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	$59.89	7.188%	$64.1949	$64.19	$64.20	$64.20
Purchase #2	$63.48	11.119%	$70.5383	$70.54	$70.55	$70.50
Purchase #3	$89.25	7.630%	$96.0598	$96.06	$96.05	$96.10
Purchase #4	$176.64	4.476%	$184.5464	$184.55	$184.55	$184.50
Purchase #5	$15.84	10.760%	$17.5444	$17.54	$17.55	$17.50
Purchase #6	$64.40	11.438%	$71.7661	$71.77	$71.75	$71.80
Purchase #7	$128.35	12.845%	$144.8366	$144.84	$144.85	$144.80
7 purchase totals =	$597.85		$649.4865	$649.49	$649.50	$649.40