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	$110.52	5.605%	$116.7146	$116.71	$116.70	$116.70
Purchase #2	$114.37	3.547%	$118.4267	$118.43	$118.45	$118.40
Purchase #3	$87.37	7.375%	$93.8135	$93.81	$93.80	$93.80
Purchase #4	$156.31	11.622%	$174.4763	$174.48	$174.50	$174.50
Purchase #5	$229.88	11.760%	$256.9139	$256.91	$256.90	$256.90
Purchase #6	$206.62	11.673%	$230.7388	$230.74	$230.75	$230.70
Purchase #7	$100.36	5.517%	$105.8969	$105.90	$105.90	$105.90
7 purchase totals =	$1,005.43		$1,096.9807	$1,096.98	$1,097.00	$1,096.90