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	$95.43	7.499%	$102.5863	$102.59	$102.60	$102.60
Purchase #2	$92.50	3.674%	$95.8985	$95.90	$95.90	$95.90
Purchase #3	$250.42	13.823%	$285.0356	$285.04	$285.05	$285.00
Purchase #4	$114.27	6.290%	$121.4576	$121.46	$121.45	$121.50
Purchase #5	$38.32	13.658%	$43.5537	$43.55	$43.55	$43.60
Purchase #6	$77.56	7.553%	$83.4181	$83.42	$83.40	$83.40
Purchase #7	$249.86	8.794%	$271.8327	$271.83	$271.85	$271.80
7 purchase totals =	$918.36		$1,003.7825	$1,003.79	$1,003.80	$1,003.80