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	$154.53	7.736%	$166.4844	$166.48	$166.50	$166.50
Purchase #2	$189.53	5.717%	$200.3654	$200.37	$200.35	$200.40
Purchase #3	$204.55	6.685%	$218.2242	$218.22	$218.20	$218.20
Purchase #4	$114.80	8.666%	$124.7486	$124.75	$124.75	$124.70
Purchase #5	$158.58	8.807%	$172.5461	$172.55	$172.55	$172.50
Purchase #6	$65.98	10.458%	$72.8802	$72.88	$72.90	$72.90
Purchase #7	$45.61	7.111%	$48.8533	$48.85	$48.85	$48.90
7 purchase totals =	$933.58		$1,004.1022	$1,004.10	$1,004.10	$1,004.10