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	$212.93	4.501%	$222.514	$222.51	$222.50	$222.50
Purchase #2	$137.50	3.162%	$141.8478	$141.85	$141.85	$141.80
Purchase #3	$29.79	8.211%	$32.2361	$32.24	$32.25	$32.20
Purchase #4	$171.62	9.474%	$187.8793	$187.88	$187.90	$187.90
Purchase #5	$6.26	13.709%	$7.1182	$7.12	$7.10	$7.10
Purchase #6	$205.56	6.731%	$219.3962	$219.40	$219.40	$219.40
Purchase #7	$78.93	8.272%	$85.4591	$85.46	$85.45	$85.50
7 purchase totals =	$842.59		$896.4507	$896.46	$896.45	$896.40