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	$187.69	4.547%	$196.2243	$196.22	$196.20	$196.20
Purchase #2	$239.73	8.522%	$260.1598	$260.16	$260.15	$260.20
Purchase #3	$87.62	3.460%	$90.6517	$90.65	$90.65	$90.70
Purchase #4	$242.45	7.196%	$259.8967	$259.90	$259.90	$259.90
Purchase #5	$146.34	3.361%	$151.2585	$151.26	$151.25	$151.30
Purchase #6	$75.62	6.371%	$80.4378	$80.44	$80.45	$80.40
Purchase #7	$30.43	11.186%	$33.8339	$33.83	$33.85	$33.80
7 purchase totals =	$1,009.88		$1,072.4627	$1,072.46	$1,072.45	$1,072.50