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	$32.90	10.538%	$36.367	$36.37	$36.35	$36.40
Purchase #2	$52.97	5.458%	$55.8611	$55.86	$55.85	$55.90
Purchase #3	$211.33	11.419%	$235.4618	$235.46	$235.45	$235.50
Purchase #4	$141.86	11.293%	$157.8802	$157.88	$157.90	$157.90
Purchase #5	$145.35	6.299%	$154.5056	$154.51	$154.50	$154.50
Purchase #6	$103.48	7.298%	$111.032	$111.03	$111.05	$111.00
Purchase #7	$194.53	12.175%	$218.214	$218.21	$218.20	$218.20
7 purchase totals =	$882.42		$969.3217	$969.32	$969.30	$969.40