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	$43.42	9.547%	$47.5653	$47.57	$47.55	$47.60
Purchase #2	$36.53	7.505%	$39.2716	$39.27	$39.25	$39.30
Purchase #3	$117.89	8.354%	$127.7385	$127.74	$127.75	$127.70
Purchase #4	$5.47	3.721%	$5.6735	$5.67	$5.65	$5.70
Purchase #5	$61.31	7.610%	$65.9757	$65.98	$66.00	$66.00
Purchase #6	$82.50	5.215%	$86.8024	$86.80	$86.80	$86.80
Purchase #7	$181.53	10.482%	$200.558	$200.56	$200.55	$200.60
7 purchase totals =	$528.65		$573.5850	$573.59	$573.55	$573.70