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	$192.83	3.792%	$200.1421	$200.14	$200.15	$200.10
Purchase #2	$115.86	13.867%	$131.9263	$131.93	$131.95	$131.90
Purchase #3	$166.89	12.188%	$187.2306	$187.23	$187.25	$187.20
Purchase #4	$197.51	5.330%	$208.0373	$208.04	$208.05	$208.00
Purchase #5	$63.33	8.173%	$68.506	$68.51	$68.50	$68.50
Purchase #6	$185.27	11.754%	$207.0466	$207.05	$207.05	$207.00
Purchase #7	$80.59	12.332%	$90.5284	$90.53	$90.55	$90.50
7 purchase totals =	$1,002.28		$1,093.4173	$1,093.43	$1,093.50	$1,093.20