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	$142.95	8.724%	$155.421	$155.42	$155.40	$155.40
Purchase #2	$227.54	12.349%	$255.6389	$255.64	$255.65	$255.60
Purchase #3	$175.80	11.763%	$196.4794	$196.48	$196.50	$196.50
Purchase #4	$242.78	3.161%	$250.4543	$250.45	$250.45	$250.50
Purchase #5	$197.77	6.304%	$210.2374	$210.24	$210.25	$210.20
Purchase #6	$103.48	5.657%	$109.3339	$109.33	$109.35	$109.30
Purchase #7	$131.87	12.252%	$148.0267	$148.03	$148.05	$148.00
7 purchase totals =	$1,222.19		$1,325.5916	$1,325.59	$1,325.65	$1,325.50