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	$118.74	7.125%	$127.2002	$127.20	$127.20	$127.20
Purchase #2	$95.32	6.245%	$101.2727	$101.27	$101.25	$101.30
Purchase #3	$44.43	4.221%	$46.3054	$46.31	$46.30	$46.30
Purchase #4	$246.38	11.217%	$274.0164	$274.02	$274.00	$274.00
Purchase #5	$85.97	12.107%	$96.3784	$96.38	$96.40	$96.40
Purchase #6	$132.45	6.823%	$141.4871	$141.49	$141.50	$141.50
Purchase #7	$138.31	10.479%	$152.8035	$152.80	$152.80	$152.80
7 purchase totals =	$861.60		$939.4637	$939.47	$939.45	$939.50