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	$41.88	3.746%	$43.4488	$43.45	$43.45	$43.40
Purchase #2	$84.97	5.379%	$89.5405	$89.54	$89.55	$89.50
Purchase #3	$134.64	10.235%	$148.4204	$148.42	$148.40	$148.40
Purchase #4	$224.54	8.204%	$242.9613	$242.96	$242.95	$243.00
Purchase #5	$28.97	8.675%	$31.4831	$31.48	$31.50	$31.50
Purchase #6	$77.81	9.719%	$85.3724	$85.37	$85.35	$85.40
Purchase #7	$114.73	4.204%	$119.5532	$119.55	$119.55	$119.60
7 purchase totals =	$707.54		$760.7797	$760.77	$760.75	$760.80