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	$117.86	9.658%	$129.2429	$129.24	$129.25	$129.20
Purchase #2	$185.51	6.175%	$196.9652	$196.97	$196.95	$197.00
Purchase #3	$100.92	10.236%	$111.2502	$111.25	$111.25	$111.30
Purchase #4	$67.88	4.437%	$70.8918	$70.89	$70.90	$70.90
Purchase #5	$80.54	4.870%	$84.4623	$84.46	$84.45	$84.50
Purchase #6	$38.27	5.823%	$40.4985	$40.50	$40.50	$40.50
Purchase #7	$154.88	8.459%	$167.9813	$167.98	$168.00	$168.00
7 purchase totals =	$745.86		$801.2922	$801.29	$801.30	$801.40