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	$189.77	5.410%	$200.0366	$200.04	$200.05	$200.00
Purchase #2	$90.27	10.843%	$100.058	$100.06	$100.05	$100.10
Purchase #3	$79.98	4.453%	$83.5415	$83.54	$83.55	$83.50
Purchase #4	$235.39	4.246%	$245.3847	$245.38	$245.40	$245.40
Purchase #5	$27.52	8.404%	$29.8328	$29.83	$29.85	$29.80
Purchase #6	$189.37	5.851%	$200.45	$200.45	$200.45	$200.50
Purchase #7	$240.98	8.569%	$261.6296	$261.63	$261.65	$261.60
7 purchase totals =	$1,053.28		$1,120.9332	$1,120.93	$1,121.00	$1,120.90