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	$143.34	7.264%	$153.7522	$153.75	$153.75	$153.80
Purchase #2	$245.69	6.566%	$261.822	$261.82	$261.80	$261.80
Purchase #3	$60.90	8.383%	$66.0052	$66.01	$66.00	$66.00
Purchase #4	$131.83	7.449%	$141.65	$141.65	$141.65	$141.70
Purchase #5	$212.40	13.448%	$240.9636	$240.96	$240.95	$241.00
Purchase #6	$64.86	13.587%	$73.6725	$73.67	$73.65	$73.70
Purchase #7	$72.52	10.440%	$80.0911	$80.09	$80.10	$80.10
7 purchase totals =	$931.54		$1,017.9566	$1,017.95	$1,017.90	$1,018.10