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	$54.50	9.667%	$59.7685	$59.77	$59.75	$59.80
Purchase #2	$97.27	3.358%	$100.5363	$100.54	$100.55	$100.50
Purchase #3	$190.69	3.189%	$196.7711	$196.77	$196.75	$196.80
Purchase #4	$185.55	10.486%	$205.0068	$205.01	$205.00	$205.00
Purchase #5	$173.51	13.436%	$196.8228	$196.82	$196.80	$196.80
Purchase #6	$136.51	8.769%	$148.4806	$148.48	$148.50	$148.50
Purchase #7	$14.57	11.782%	$16.2866	$16.29	$16.30	$16.30
7 purchase totals =	$852.60		$923.6727	$923.68	$923.65	$923.70