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	$82.84	10.684%	$91.6906	$91.69	$91.70	$91.70
Purchase #2	$222.34	5.450%	$234.4575	$234.46	$234.45	$234.50
Purchase #3	$49.50	10.396%	$54.646	$54.65	$54.65	$54.60
Purchase #4	$195.58	10.633%	$216.376	$216.38	$216.40	$216.40
Purchase #5	$222.85	10.835%	$246.9958	$247.00	$247.00	$247.00
Purchase #6	$151.97	12.789%	$171.4054	$171.41	$171.40	$171.40
Purchase #7	$150.45	4.193%	$156.7584	$156.76	$156.75	$156.80
7 purchase totals =	$1,075.53		$1,172.3297	$1,172.35	$1,172.35	$1,172.40