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	$13.97	9.226%	$15.2589	$15.26	$15.25	$15.30
Purchase #2	$199.86	11.272%	$222.3882	$222.39	$222.40	$222.40
Purchase #3	$119.88	9.764%	$131.5851	$131.59	$131.60	$131.60
Purchase #4	$112.50	11.324%	$125.2395	$125.24	$125.25	$125.20
Purchase #5	$139.53	6.190%	$148.1669	$148.17	$148.15	$148.20
Purchase #6	$55.82	6.537%	$59.469	$59.47	$59.45	$59.50
Purchase #7	$189.73	11.545%	$211.6343	$211.63	$211.65	$211.60
7 purchase totals =	$831.29		$913.7419	$913.75	$913.75	$913.80