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	$77.72	12.506%	$87.4397	$87.44	$87.45	$87.40
Purchase #2	$116.97	13.121%	$132.3176	$132.32	$132.30	$132.30
Purchase #3	$94.47	8.598%	$102.5925	$102.59	$102.60	$102.60
Purchase #4	$171.31	7.682%	$184.47	$184.47	$184.45	$184.50
Purchase #5	$194.62	10.191%	$214.4537	$214.45	$214.45	$214.50
Purchase #6	$250.88	5.258%	$264.0713	$264.07	$264.05	$264.10
Purchase #7	$187.82	12.503%	$211.3031	$211.30	$211.30	$211.30
7 purchase totals =	$1,093.79		$1,196.6479	$1,196.64	$1,196.60	$1,196.70