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	$83.29	7.112%	$89.2136	$89.21	$89.20	$89.20
Purchase #2	$208.92	5.222%	$219.8298	$219.83	$219.85	$219.80
Purchase #3	$62.94	7.637%	$67.7467	$67.75	$67.75	$67.70
Purchase #4	$82.75	13.853%	$94.2134	$94.21	$94.20	$94.20
Purchase #5	$198.39	13.716%	$225.6012	$225.60	$225.60	$225.60
Purchase #6	$122.56	8.192%	$132.6001	$132.60	$132.60	$132.60
Purchase #7	$52.33	13.807%	$59.5552	$59.56	$59.55	$59.60
7 purchase totals =	$811.18		$888.7600	$888.76	$888.75	$888.70