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	$164.89	4.268%	$171.9275	$171.93	$171.95	$171.90
Purchase #2	$208.72	3.673%	$216.3863	$216.39	$216.40	$216.40
Purchase #3	$17.76	7.658%	$19.1201	$19.12	$19.10	$19.10
Purchase #4	$163.83	6.354%	$174.2398	$174.24	$174.25	$174.20
Purchase #5	$91.38	4.630%	$95.6109	$95.61	$95.60	$95.60
Purchase #6	$30.83	12.188%	$34.5876	$34.59	$34.60	$34.60
Purchase #7	$74.88	4.462%	$78.2211	$78.22	$78.20	$78.20
7 purchase totals =	$752.29		$790.0933	$790.10	$790.10	$790.00