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	$194.43	5.586%	$205.2909	$205.29	$205.30	$205.30
Purchase #2	$219.87	13.479%	$249.5063	$249.51	$249.50	$249.50
Purchase #3	$175.48	6.496%	$186.8792	$186.88	$186.90	$186.90
Purchase #4	$44.43	7.721%	$47.8604	$47.86	$47.85	$47.90
Purchase #5	$118.37	4.652%	$123.8766	$123.88	$123.90	$123.90
Purchase #6	$123.57	7.618%	$132.9836	$132.98	$133.00	$133.00
Purchase #7	$55.34	10.629%	$61.2221	$61.22	$61.20	$61.20
7 purchase totals =	$931.49		$1,007.6191	$1,007.62	$1,007.65	$1,007.70