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	$224.41	5.832%	$237.4976	$237.50	$237.50	$237.50
Purchase #2	$6.91	13.748%	$7.86	$7.86	$7.85	$7.90
Purchase #3	$102.91	3.204%	$106.2072	$106.21	$106.20	$106.20
Purchase #4	$125.32	13.207%	$141.871	$141.87	$141.85	$141.90
Purchase #5	$168.86	8.144%	$182.612	$182.61	$182.60	$182.60
Purchase #6	$115.54	13.617%	$131.2731	$131.27	$131.25	$131.30
Purchase #7	$78.74	13.613%	$89.4589	$89.46	$89.45	$89.50
7 purchase totals =	$822.69		$896.7798	$896.78	$896.70	$896.90