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	$150.45	5.856%	$159.2604	$159.26	$159.25	$159.30
Purchase #2	$118.26	10.146%	$130.2587	$130.26	$130.25	$130.30
Purchase #3	$116.53	11.637%	$130.0906	$130.09	$130.10	$130.10
Purchase #4	$13.59	3.812%	$14.1081	$14.11	$14.10	$14.10
Purchase #5	$248.47	12.517%	$279.571	$279.57	$279.55	$279.60
Purchase #6	$168.64	7.144%	$180.6876	$180.69	$180.70	$180.70
Purchase #7	$190.98	13.849%	$217.4288	$217.43	$217.45	$217.40
7 purchase totals =	$1,006.92		$1,111.4052	$1,111.41	$1,111.40	$1,111.50