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	$148.36	11.121%	$164.8591	$164.86	$164.85	$164.90
Purchase #2	$55.85	3.661%	$57.8947	$57.89	$57.90	$57.90
Purchase #3	$23.85	6.429%	$25.3833	$25.38	$25.40	$25.40
Purchase #4	$197.90	7.579%	$212.8988	$212.90	$212.90	$212.90
Purchase #5	$210.51	3.402%	$217.6716	$217.67	$217.65	$217.70
Purchase #6	$156.96	6.603%	$167.3241	$167.32	$167.30	$167.30
Purchase #7	$66.67	12.284%	$74.8597	$74.86	$74.85	$74.90
7 purchase totals =	$860.10		$920.8913	$920.88	$920.85	$921.00