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	$42.42	3.139%	$43.7516	$43.75	$43.75	$43.80
Purchase #2	$89.35	7.693%	$96.2237	$96.22	$96.20	$96.20
Purchase #3	$73.75	6.509%	$78.5504	$78.55	$78.55	$78.60
Purchase #4	$215.78	4.352%	$225.1707	$225.17	$225.15	$225.20
Purchase #5	$56.59	13.675%	$64.3287	$64.33	$64.35	$64.30
Purchase #6	$191.81	4.455%	$200.3551	$200.36	$200.35	$200.40
Purchase #7	$55.31	10.203%	$60.9533	$60.95	$60.95	$61.00
7 purchase totals =	$725.01		$769.3335	$769.33	$769.30	$769.50