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	$146.41	12.196%	$164.2662	$164.27	$164.25	$164.30
Purchase #2	$62.70	8.283%	$67.8934	$67.89	$67.90	$67.90
Purchase #3	$131.90	8.325%	$142.8807	$142.88	$142.90	$142.90
Purchase #4	$187.61	12.246%	$210.5847	$210.58	$210.60	$210.60
Purchase #5	$243.59	11.697%	$272.0827	$272.08	$272.10	$272.10
Purchase #6	$185.34	4.327%	$193.3597	$193.36	$193.35	$193.40
Purchase #7	$82.34	13.461%	$93.4238	$93.42	$93.40	$93.40
7 purchase totals =	$1,039.89		$1,144.4912	$1,144.48	$1,144.50	$1,144.60