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	$223.32	12.607%	$251.474	$251.47	$251.45	$251.50
Purchase #2	$164.32	9.328%	$179.6478	$179.65	$179.65	$179.60
Purchase #3	$162.58	11.526%	$181.319	$181.32	$181.30	$181.30
Purchase #4	$216.47	3.691%	$224.4599	$224.46	$224.45	$224.50
Purchase #5	$131.64	4.308%	$137.3111	$137.31	$137.30	$137.30
Purchase #6	$74.82	8.282%	$81.0166	$81.02	$81.00	$81.00
Purchase #7	$172.88	13.592%	$196.3778	$196.38	$196.40	$196.40
7 purchase totals =	$1,146.03		$1,251.6062	$1,251.61	$1,251.55	$1,251.60