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	$205.44	8.722%	$223.3585	$223.36	$223.35	$223.40
Purchase #2	$26.64	10.138%	$29.3408	$29.34	$29.35	$29.30
Purchase #3	$181.63	11.266%	$202.0924	$202.09	$202.10	$202.10
Purchase #4	$123.78	5.838%	$131.0063	$131.01	$131.00	$131.00
Purchase #5	$215.56	3.585%	$223.2878	$223.29	$223.30	$223.30
Purchase #6	$38.70	5.442%	$40.8061	$40.81	$40.80	$40.80
Purchase #7	$241.71	3.695%	$250.6412	$250.64	$250.65	$250.60
7 purchase totals =	$1,033.46		$1,100.5331	$1,100.54	$1,100.55	$1,100.50