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	$106.51	10.732%	$117.9407	$117.94	$117.95	$117.90
Purchase #2	$159.64	10.592%	$176.5491	$176.55	$176.55	$176.50
Purchase #3	$197.76	4.387%	$206.4357	$206.44	$206.45	$206.40
Purchase #4	$57.64	3.616%	$59.7243	$59.72	$59.70	$59.70
Purchase #5	$139.95	11.463%	$155.9925	$155.99	$156.00	$156.00
Purchase #6	$47.27	9.318%	$51.6746	$51.67	$51.65	$51.70
Purchase #7	$78.90	13.171%	$89.2919	$89.29	$89.30	$89.30
7 purchase totals =	$787.67		$857.6088	$857.60	$857.60	$857.50