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	$231.75	5.781%	$245.1475	$245.15	$245.15	$245.10
Purchase #2	$189.59	3.235%	$195.7232	$195.72	$195.70	$195.70
Purchase #3	$110.45	7.367%	$118.5869	$118.59	$118.60	$118.60
Purchase #4	$89.31	12.127%	$100.1406	$100.14	$100.15	$100.10
Purchase #5	$67.83	4.318%	$70.7589	$70.76	$70.75	$70.80
Purchase #6	$87.54	12.757%	$98.7075	$98.71	$98.70	$98.70
Purchase #7	$170.97	6.347%	$181.8215	$181.82	$181.80	$181.80
7 purchase totals =	$947.44		$1,010.8861	$1,010.89	$1,010.85	$1,010.80