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	$114.92	10.871%	$127.413	$127.41	$127.40	$127.40
Purchase #2	$189.31	8.427%	$205.2632	$205.26	$205.25	$205.30
Purchase #3	$51.92	13.785%	$59.0772	$59.08	$59.10	$59.10
Purchase #4	$189.47	7.104%	$202.9299	$202.93	$202.95	$202.90
Purchase #5	$208.26	13.867%	$237.1394	$237.14	$237.15	$237.10
Purchase #6	$94.51	5.300%	$99.519	$99.52	$99.50	$99.50
Purchase #7	$59.96	12.302%	$67.3363	$67.34	$67.35	$67.30
7 purchase totals =	$908.35		$998.6780	$998.68	$998.70	$998.60