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	$40.87	12.187%	$45.8508	$45.85	$45.85	$45.90
Purchase #2	$44.57	8.596%	$48.4012	$48.40	$48.40	$48.40
Purchase #3	$162.61	7.399%	$174.6415	$174.64	$174.65	$174.60
Purchase #4	$176.99	11.164%	$196.7492	$196.75	$196.75	$196.70
Purchase #5	$242.82	5.290%	$255.6652	$255.67	$255.65	$255.70
Purchase #6	$48.89	5.712%	$51.6826	$51.68	$51.70	$51.70
Purchase #7	$86.58	6.224%	$91.9687	$91.97	$91.95	$92.00
7 purchase totals =	$803.33		$864.9592	$864.96	$864.95	$865.00