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	$109.94	8.838%	$119.6565	$119.66	$119.65	$119.70
Purchase #2	$117.65	12.819%	$132.7316	$132.73	$132.75	$132.70
Purchase #3	$241.91	4.861%	$253.6692	$253.67	$253.65	$253.70
Purchase #4	$91.48	13.366%	$103.7072	$103.71	$103.70	$103.70
Purchase #5	$71.54	9.440%	$78.2934	$78.29	$78.30	$78.30
Purchase #6	$239.38	3.633%	$248.0767	$248.08	$248.10	$248.10
Purchase #7	$209.82	6.445%	$223.3429	$223.34	$223.35	$223.30
7 purchase totals =	$1,081.72		$1,159.4775	$1,159.48	$1,159.50	$1,159.50