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	$68.34	3.353%	$70.6314	$70.63	$70.65	$70.60
Purchase #2	$29.43	13.374%	$33.366	$33.37	$33.35	$33.40
Purchase #3	$10.47	12.308%	$11.7586	$11.76	$11.75	$11.80
Purchase #4	$73.68	6.569%	$78.52	$78.52	$78.50	$78.50
Purchase #5	$219.46	6.661%	$234.0782	$234.08	$234.10	$234.10
Purchase #6	$19.80	10.816%	$21.9416	$21.94	$21.95	$21.90
Purchase #7	$69.49	13.561%	$78.9135	$78.91	$78.90	$78.90
7 purchase totals =	$490.67		$529.2093	$529.21	$529.20	$529.20