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	$37.54	10.833%	$41.6067	$41.61	$41.60	$41.60
Purchase #2	$163.80	4.854%	$171.7509	$171.75	$171.75	$171.80
Purchase #3	$103.89	5.680%	$109.791	$109.79	$109.80	$109.80
Purchase #4	$235.55	9.862%	$258.7799	$258.78	$258.80	$258.80
Purchase #5	$69.33	10.861%	$76.8599	$76.86	$76.85	$76.90
Purchase #6	$128.97	6.413%	$137.2408	$137.24	$137.25	$137.20
Purchase #7	$88.82	10.729%	$98.3495	$98.35	$98.35	$98.30
7 purchase totals =	$827.90		$894.3787	$894.38	$894.40	$894.40