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	$247.61	6.363%	$263.3654	$263.37	$263.35	$263.40
Purchase #2	$50.71	7.846%	$54.6887	$54.69	$54.70	$54.70
Purchase #3	$187.43	11.462%	$208.9132	$208.91	$208.90	$208.90
Purchase #4	$13.44	12.530%	$15.124	$15.12	$15.10	$15.10
Purchase #5	$158.69	6.812%	$169.5	$169.50	$169.50	$169.50
Purchase #6	$172.78	3.738%	$179.2385	$179.24	$179.25	$179.20
Purchase #7	$228.31	5.447%	$240.746	$240.75	$240.75	$240.70
7 purchase totals =	$1,058.97		$1,131.5758	$1,131.58	$1,131.55	$1,131.50