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	$118.52	6.154%	$125.8137	$125.81	$125.80	$125.80
Purchase #2	$146.96	6.199%	$156.0701	$156.07	$156.05	$156.10
Purchase #3	$39.55	10.709%	$43.7854	$43.79	$43.80	$43.80
Purchase #4	$235.65	5.798%	$249.313	$249.31	$249.30	$249.30
Purchase #5	$101.75	6.424%	$108.2864	$108.29	$108.30	$108.30
Purchase #6	$233.50	13.873%	$265.8935	$265.89	$265.90	$265.90
Purchase #7	$93.63	7.727%	$100.8648	$100.86	$100.85	$100.90
7 purchase totals =	$969.56		$1,050.0269	$1,050.02	$1,050.00	$1,050.10