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	$206.61	3.264%	$213.3538	$213.35	$213.35	$213.40
Purchase #2	$13.71	10.474%	$15.146	$15.15	$15.15	$15.10
Purchase #3	$41.54	10.264%	$45.8037	$45.80	$45.80	$45.80
Purchase #4	$225.46	13.307%	$255.462	$255.46	$255.45	$255.50
Purchase #5	$64.89	11.155%	$72.1285	$72.13	$72.15	$72.10
Purchase #6	$185.80	13.817%	$211.472	$211.47	$211.45	$211.50
Purchase #7	$79.30	3.808%	$82.3197	$82.32	$82.30	$82.30
7 purchase totals =	$817.31		$895.6857	$895.68	$895.65	$895.70