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	$208.61	7.623%	$224.5123	$224.51	$224.50	$224.50
Purchase #2	$54.81	3.363%	$56.6533	$56.65	$56.65	$56.70
Purchase #3	$47.56	13.805%	$54.1257	$54.13	$54.15	$54.10
Purchase #4	$82.88	12.860%	$93.5384	$93.54	$93.55	$93.50
Purchase #5	$47.38	7.193%	$50.788	$50.79	$50.80	$50.80
Purchase #6	$41.38	3.745%	$42.9297	$42.93	$42.95	$42.90
Purchase #7	$75.81	10.474%	$83.7503	$83.75	$83.75	$83.80
7 purchase totals =	$558.43		$606.2977	$606.30	$606.35	$606.30