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	$227.64	5.625%	$240.4448	$240.44	$240.45	$240.40
Purchase #2	$169.94	11.646%	$189.7312	$189.73	$189.75	$189.70
Purchase #3	$113.84	8.806%	$123.8648	$123.86	$123.85	$123.90
Purchase #4	$147.62	7.705%	$158.9941	$158.99	$159.00	$159.00
Purchase #5	$134.58	13.596%	$152.8775	$152.88	$152.90	$152.90
Purchase #6	$79.86	3.441%	$82.608	$82.61	$82.60	$82.60
Purchase #7	$110.82	6.787%	$118.3414	$118.34	$118.35	$118.30
7 purchase totals =	$984.30		$1,066.8618	$1,066.85	$1,066.90	$1,066.80