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	$142.39	12.864%	$160.707	$160.71	$160.70	$160.70
Purchase #2	$14.73	11.573%	$16.4347	$16.43	$16.45	$16.40
Purchase #3	$39.93	7.673%	$42.9938	$42.99	$43.00	$43.00
Purchase #4	$85.67	4.371%	$89.4146	$89.41	$89.40	$89.40
Purchase #5	$81.56	12.186%	$91.4989	$91.50	$91.50	$91.50
Purchase #6	$13.30	4.526%	$13.902	$13.90	$13.90	$13.90
Purchase #7	$23.56	7.293%	$25.2782	$25.28	$25.30	$25.30
7 purchase totals =	$401.14		$440.2292	$440.22	$440.25	$440.20