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	$209.57	13.130%	$237.0865	$237.09	$237.10	$237.10
Purchase #2	$30.64	10.656%	$33.905	$33.91	$33.90	$33.90
Purchase #3	$99.92	10.761%	$110.6724	$110.67	$110.65	$110.70
Purchase #4	$103.60	7.571%	$111.4436	$111.44	$111.45	$111.40
Purchase #5	$16.43	12.454%	$18.4762	$18.48	$18.50	$18.50
Purchase #6	$136.75	3.398%	$141.3968	$141.40	$141.40	$141.40
Purchase #7	$216.60	5.481%	$228.4718	$228.47	$228.45	$228.50
7 purchase totals =	$813.51		$881.4523	$881.46	$881.45	$881.50