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	$90.63	4.569%	$94.7709	$94.77	$94.75	$94.80
Purchase #2	$74.61	10.558%	$82.4873	$82.49	$82.50	$82.50
Purchase #3	$140.55	5.466%	$148.2325	$148.23	$148.25	$148.20
Purchase #4	$146.80	13.141%	$166.091	$166.09	$166.10	$166.10
Purchase #5	$235.98	9.731%	$258.9432	$258.94	$258.95	$258.90
Purchase #6	$160.79	13.520%	$182.5288	$182.53	$182.55	$182.50
Purchase #7	$231.89	10.511%	$256.264	$256.26	$256.25	$256.30
7 purchase totals =	$1,081.25		$1,189.3177	$1,189.31	$1,189.35	$1,189.30