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	$186.29	8.160%	$201.4913	$201.49	$201.50	$201.50
Purchase #2	$139.91	13.867%	$159.3113	$159.31	$159.30	$159.30
Purchase #3	$69.84	11.600%	$77.9414	$77.94	$77.95	$77.90
Purchase #4	$43.53	4.179%	$45.3491	$45.35	$45.35	$45.30
Purchase #5	$188.26	6.725%	$200.9205	$200.92	$200.90	$200.90
Purchase #6	$157.63	10.555%	$174.2678	$174.27	$174.25	$174.30
Purchase #7	$145.46	10.197%	$160.2926	$160.29	$160.30	$160.30
7 purchase totals =	$930.92		$1,019.5740	$1,019.57	$1,019.55	$1,019.50