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	$101.50	9.791%	$111.4379	$111.44	$111.45	$111.40
Purchase #2	$232.63	3.411%	$240.565	$240.57	$240.55	$240.60
Purchase #3	$130.35	11.104%	$144.8241	$144.82	$144.80	$144.80
Purchase #4	$50.69	5.362%	$53.408	$53.41	$53.40	$53.40
Purchase #5	$59.60	6.137%	$63.2577	$63.26	$63.25	$63.30
Purchase #6	$77.61	3.780%	$80.5437	$80.54	$80.55	$80.50
Purchase #7	$109.44	11.722%	$122.2686	$122.27	$122.25	$122.30
7 purchase totals =	$761.82		$816.3050	$816.31	$816.25	$816.30