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	$101.98	11.111%	$113.311	$113.31	$113.30	$113.30
Purchase #2	$248.92	3.686%	$258.0952	$258.10	$258.10	$258.10
Purchase #3	$195.29	7.846%	$210.6125	$210.61	$210.60	$210.60
Purchase #4	$56.25	9.506%	$61.5971	$61.60	$61.60	$61.60
Purchase #5	$6.43	10.252%	$7.0892	$7.09	$7.10	$7.10
Purchase #6	$198.35	9.516%	$217.225	$217.23	$217.25	$217.20
Purchase #7	$109.55	3.573%	$113.4642	$113.46	$113.45	$113.50
7 purchase totals =	$916.77		$981.3942	$981.40	$981.40	$981.40