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	$127.95	10.387%	$141.2402	$141.24	$141.25	$141.20
Purchase #2	$53.98	5.748%	$57.0828	$57.08	$57.10	$57.10
Purchase #3	$37.57	11.127%	$41.7504	$41.75	$41.75	$41.80
Purchase #4	$208.85	13.136%	$236.2845	$236.28	$236.30	$236.30
Purchase #5	$187.33	13.474%	$212.5708	$212.57	$212.55	$212.60
Purchase #6	$29.56	6.732%	$31.55	$31.55	$31.55	$31.60
Purchase #7	$250.31	11.629%	$279.4185	$279.42	$279.40	$279.40
7 purchase totals =	$895.55		$999.8972	$999.89	$999.90	$1,000.00