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	$166.41	9.343%	$181.9577	$181.96	$181.95	$182.00
Purchase #2	$90.71	11.111%	$100.7888	$100.79	$100.80	$100.80
Purchase #3	$29.47	7.480%	$31.6744	$31.67	$31.65	$31.70
Purchase #4	$81.76	10.785%	$90.5778	$90.58	$90.60	$90.60
Purchase #5	$181.49	4.802%	$190.2051	$190.21	$190.20	$190.20
Purchase #6	$5.41	6.854%	$5.7808	$5.78	$5.80	$5.80
Purchase #7	$52.57	4.774%	$55.0797	$55.08	$55.10	$55.10
7 purchase totals =	$607.82		$656.0643	$656.07	$656.10	$656.20