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	$10.55	6.219%	$11.2061	$11.21	$11.20	$11.20
Purchase #2	$59.50	3.217%	$61.4141	$61.41	$61.40	$61.40
Purchase #3	$41.72	8.423%	$45.2341	$45.23	$45.25	$45.20
Purchase #4	$118.43	12.521%	$133.2586	$133.26	$133.25	$133.30
Purchase #5	$69.63	3.447%	$72.0301	$72.03	$72.05	$72.00
Purchase #6	$27.44	13.257%	$31.0777	$31.08	$31.10	$31.10
Purchase #7	$82.42	5.441%	$86.9045	$86.90	$86.90	$86.90
7 purchase totals =	$409.69		$441.1252	$441.12	$441.15	$441.10