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	$209.50	7.627%	$225.4786	$225.48	$225.50	$225.50
Purchase #2	$200.57	7.306%	$215.2236	$215.22	$215.20	$215.20
Purchase #3	$130.41	6.446%	$138.8162	$138.82	$138.80	$138.80
Purchase #4	$77.35	10.326%	$85.3372	$85.34	$85.35	$85.30
Purchase #5	$155.97	10.453%	$172.2735	$172.27	$172.25	$172.30
Purchase #6	$109.57	3.186%	$113.0609	$113.06	$113.05	$113.10
Purchase #7	$28.52	10.140%	$31.4119	$31.41	$31.40	$31.40
7 purchase totals =	$911.89		$981.6019	$981.60	$981.55	$981.60