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	$209.43	13.792%	$238.3146	$238.31	$238.30	$238.30
Purchase #2	$76.57	7.803%	$82.5448	$82.54	$82.55	$82.50
Purchase #3	$215.37	9.295%	$235.3886	$235.39	$235.40	$235.40
Purchase #4	$86.58	3.195%	$89.3462	$89.35	$89.35	$89.30
Purchase #5	$161.92	3.365%	$167.3686	$167.37	$167.35	$167.40
Purchase #6	$203.91	6.696%	$217.5638	$217.56	$217.55	$217.60
Purchase #7	$195.43	11.111%	$217.1442	$217.14	$217.15	$217.10
7 purchase totals =	$1,149.21		$1,247.6708	$1,247.66	$1,247.65	$1,247.60