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	$193.60	11.318%	$215.5116	$215.51	$215.50	$215.50
Purchase #2	$101.40	8.127%	$109.6408	$109.64	$109.65	$109.60
Purchase #3	$132.50	8.158%	$143.3094	$143.31	$143.30	$143.30
Purchase #4	$77.87	7.534%	$83.7367	$83.74	$83.75	$83.70
Purchase #5	$78.95	13.362%	$89.4993	$89.50	$89.50	$89.50
Purchase #6	$149.96	5.648%	$158.4297	$158.43	$158.45	$158.40
Purchase #7	$92.50	3.164%	$95.4267	$95.43	$95.45	$95.40
7 purchase totals =	$826.78		$895.5542	$895.56	$895.60	$895.40