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	$91.77	9.804%	$100.7671	$100.77	$100.75	$100.80
Purchase #2	$165.31	6.230%	$175.6088	$175.61	$175.60	$175.60
Purchase #3	$55.58	10.638%	$61.4926	$61.49	$61.50	$61.50
Purchase #4	$73.93	5.212%	$77.7832	$77.78	$77.80	$77.80
Purchase #5	$10.44	5.306%	$10.9939	$10.99	$11.00	$11.00
Purchase #6	$37.48	7.859%	$40.4256	$40.43	$40.45	$40.40
Purchase #7	$196.30	6.499%	$209.0575	$209.06	$209.05	$209.10
7 purchase totals =	$630.81		$676.1287	$676.13	$676.15	$676.20