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	$61.49	6.815%	$65.6805	$65.68	$65.70	$65.70
Purchase #2	$81.46	5.687%	$86.0926	$86.09	$86.10	$86.10
Purchase #3	$244.97	12.494%	$275.5766	$275.58	$275.60	$275.60
Purchase #4	$117.49	5.398%	$123.8321	$123.83	$123.85	$123.80
Purchase #5	$70.68	6.866%	$75.5329	$75.53	$75.55	$75.50
Purchase #6	$245.95	3.816%	$255.3355	$255.34	$255.35	$255.30
Purchase #7	$131.78	11.484%	$146.9136	$146.91	$146.90	$146.90
7 purchase totals =	$953.82		$1,028.9638	$1,028.96	$1,029.05	$1,028.90