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	$38.69	11.505%	$43.1413	$43.14	$43.15	$43.10
Purchase #2	$227.75	12.483%	$256.18	$256.18	$256.20	$256.20
Purchase #3	$17.91	7.714%	$19.2916	$19.29	$19.30	$19.30
Purchase #4	$198.41	6.389%	$211.0864	$211.09	$211.10	$211.10
Purchase #5	$83.37	11.105%	$92.6282	$92.63	$92.65	$92.60
Purchase #6	$212.46	11.774%	$237.475	$237.48	$237.50	$237.50
Purchase #7	$196.89	12.693%	$221.8812	$221.88	$221.90	$221.90
7 purchase totals =	$975.48		$1,081.6837	$1,081.69	$1,081.80	$1,081.70