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	$147.41	5.463%	$155.463	$155.46	$155.45	$155.50
Purchase #2	$50.59	11.438%	$56.3765	$56.38	$56.40	$56.40
Purchase #3	$235.55	3.197%	$243.0805	$243.08	$243.10	$243.10
Purchase #4	$41.71	11.732%	$46.6034	$46.60	$46.60	$46.60
Purchase #5	$238.71	7.545%	$256.7207	$256.72	$256.70	$256.70
Purchase #6	$51.63	13.412%	$58.5546	$58.55	$58.55	$58.60
Purchase #7	$198.93	13.347%	$225.4812	$225.48	$225.50	$225.50
7 purchase totals =	$964.53		$1,042.2799	$1,042.27	$1,042.30	$1,042.40