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	$13.58	8.351%	$14.7141	$14.71	$14.70	$14.70
Purchase #2	$30.27	3.220%	$31.2447	$31.24	$31.25	$31.20
Purchase #3	$194.45	7.389%	$208.8179	$208.82	$208.80	$208.80
Purchase #4	$168.56	6.540%	$179.5838	$179.58	$179.60	$179.60
Purchase #5	$110.34	3.659%	$114.3773	$114.38	$114.40	$114.40
Purchase #6	$146.91	5.681%	$155.256	$155.26	$155.25	$155.30
Purchase #7	$156.45	7.675%	$168.4575	$168.46	$168.45	$168.50
7 purchase totals =	$820.56		$872.4513	$872.45	$872.45	$872.50