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	$112.46	4.417%	$117.4274	$117.43	$117.45	$117.40
Purchase #2	$70.66	9.501%	$77.3734	$77.37	$77.35	$77.40
Purchase #3	$110.82	3.542%	$114.7452	$114.75	$114.75	$114.70
Purchase #4	$230.54	3.153%	$237.8089	$237.81	$237.80	$237.80
Purchase #5	$181.58	5.705%	$191.9391	$191.94	$191.95	$191.90
Purchase #6	$214.60	9.458%	$234.8969	$234.90	$234.90	$234.90
Purchase #7	$82.45	9.517%	$90.2968	$90.30	$90.30	$90.30
7 purchase totals =	$1,003.11		$1,064.4877	$1,064.50	$1,064.50	$1,064.40