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	$124.41	13.564%	$141.285	$141.29	$141.30	$141.30
Purchase #2	$206.43	7.221%	$221.3363	$221.34	$221.35	$221.30
Purchase #3	$116.42	13.168%	$131.7502	$131.75	$131.75	$131.80
Purchase #4	$178.79	6.554%	$190.5079	$190.51	$190.50	$190.50
Purchase #5	$136.96	3.302%	$141.4824	$141.48	$141.50	$141.50
Purchase #6	$120.39	9.508%	$131.8367	$131.84	$131.85	$131.80
Purchase #7	$211.33	4.813%	$221.5013	$221.50	$221.50	$221.50
7 purchase totals =	$1,094.73		$1,179.6998	$1,179.71	$1,179.75	$1,179.70