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	$70.88	3.520%	$73.375	$73.38	$73.40	$73.40
Purchase #2	$43.85	5.553%	$46.285	$46.29	$46.30	$46.30
Purchase #3	$35.77	7.498%	$38.452	$38.45	$38.45	$38.50
Purchase #4	$90.81	7.347%	$97.4818	$97.48	$97.50	$97.50
Purchase #5	$131.78	5.662%	$139.2414	$139.24	$139.25	$139.20
Purchase #6	$234.82	11.650%	$262.1765	$262.18	$262.20	$262.20
Purchase #7	$50.57	13.187%	$57.2387	$57.24	$57.25	$57.20
7 purchase totals =	$658.48		$714.2504	$714.26	$714.35	$714.30