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	$88.81	4.561%	$92.8606	$92.86	$92.85	$92.90
Purchase #2	$152.79	10.402%	$168.6832	$168.68	$168.70	$168.70
Purchase #3	$20.45	4.496%	$21.3694	$21.37	$21.35	$21.40
Purchase #4	$115.47	3.449%	$119.4526	$119.45	$119.45	$119.50
Purchase #5	$57.44	7.764%	$61.8996	$61.90	$61.90	$61.90
Purchase #6	$207.46	6.473%	$220.8889	$220.89	$220.90	$220.90
Purchase #7	$6.36	12.205%	$7.1362	$7.14	$7.15	$7.10
7 purchase totals =	$648.78		$692.2905	$692.29	$692.30	$692.40