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	$224.92	11.266%	$250.2595	$250.26	$250.25	$250.30
Purchase #2	$109.41	4.310%	$114.1256	$114.13	$114.15	$114.10
Purchase #3	$192.44	3.310%	$198.8098	$198.81	$198.80	$198.80
Purchase #4	$121.77	8.192%	$131.7454	$131.75	$131.75	$131.70
Purchase #5	$40.38	13.327%	$45.7614	$45.76	$45.75	$45.80
Purchase #6	$72.86	13.640%	$82.7981	$82.80	$82.80	$82.80
Purchase #7	$160.65	11.762%	$179.5457	$179.55	$179.55	$179.50
7 purchase totals =	$922.43		$1,003.0455	$1,003.06	$1,003.05	$1,003.00