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	$108.60	11.286%	$120.8566	$120.86	$120.85	$120.90
Purchase #2	$131.46	11.813%	$146.9894	$146.99	$147.00	$147.00
Purchase #3	$63.40	13.334%	$71.8538	$71.85	$71.85	$71.90
Purchase #4	$56.37	8.339%	$61.0707	$61.07	$61.05	$61.10
Purchase #5	$136.30	10.538%	$150.6633	$150.66	$150.65	$150.70
Purchase #6	$223.64	11.368%	$249.0634	$249.06	$249.05	$249.10
Purchase #7	$190.82	10.818%	$211.4629	$211.46	$211.45	$211.50
7 purchase totals =	$910.59		$1,011.9601	$1,011.95	$1,011.90	$1,012.20