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	$76.64	12.748%	$86.4101	$86.41	$86.40	$86.40
Purchase #2	$161.90	12.588%	$182.28	$182.28	$182.30	$182.30
Purchase #3	$223.46	12.308%	$250.9635	$250.96	$250.95	$251.00
Purchase #4	$175.64	9.577%	$192.461	$192.46	$192.45	$192.50
Purchase #5	$162.56	10.387%	$179.4451	$179.45	$179.45	$179.40
Purchase #6	$164.61	7.301%	$176.6282	$176.63	$176.65	$176.60
Purchase #7	$96.91	8.597%	$105.2414	$105.24	$105.25	$105.20
7 purchase totals =	$1,061.72		$1,173.4293	$1,173.43	$1,173.45	$1,173.40