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	$218.40	10.131%	$240.5261	$240.53	$240.55	$240.50
Purchase #2	$178.42	13.833%	$203.1008	$203.10	$203.10	$203.10
Purchase #3	$153.58	10.623%	$169.8948	$169.89	$169.90	$169.90
Purchase #4	$222.73	7.249%	$238.8757	$238.88	$238.90	$238.90
Purchase #5	$111.90	6.261%	$118.9061	$118.91	$118.90	$118.90
Purchase #6	$55.64	3.542%	$57.6108	$57.61	$57.60	$57.60
Purchase #7	$141.71	12.377%	$159.2494	$159.25	$159.25	$159.20
7 purchase totals =	$1,082.38		$1,188.1637	$1,188.17	$1,188.20	$1,188.10