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	$7.33	3.760%	$7.6056	$7.61	$7.60	$7.60
Purchase #2	$158.89	6.718%	$169.5642	$169.56	$169.55	$169.60
Purchase #3	$153.76	13.314%	$174.2316	$174.23	$174.25	$174.20
Purchase #4	$59.82	6.650%	$63.798	$63.80	$63.80	$63.80
Purchase #5	$104.78	7.409%	$112.5432	$112.54	$112.55	$112.50
Purchase #6	$158.54	4.595%	$165.8249	$165.82	$165.80	$165.80
Purchase #7	$218.51	5.287%	$230.0626	$230.06	$230.05	$230.10
7 purchase totals =	$861.63		$923.6301	$923.62	$923.60	$923.60