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	$33.62	4.548%	$35.149	$35.15	$35.15	$35.10
Purchase #2	$12.97	12.300%	$14.5653	$14.57	$14.55	$14.60
Purchase #3	$29.45	3.310%	$30.4248	$30.42	$30.40	$30.40
Purchase #4	$94.58	4.487%	$98.8238	$98.82	$98.80	$98.80
Purchase #5	$83.74	7.259%	$89.8187	$89.82	$89.80	$89.80
Purchase #6	$51.73	6.464%	$55.0738	$55.07	$55.05	$55.10
Purchase #7	$130.73	12.274%	$146.7758	$146.78	$146.80	$146.80
7 purchase totals =	$436.82		$470.6312	$470.63	$470.55	$470.60