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	$157.49	4.304%	$164.2684	$164.27	$164.25	$164.30
Purchase #2	$155.64	11.207%	$173.0826	$173.08	$173.10	$173.10
Purchase #3	$122.59	11.142%	$136.249	$136.25	$136.25	$136.20
Purchase #4	$178.78	8.624%	$194.198	$194.20	$194.20	$194.20
Purchase #5	$59.76	7.846%	$64.4488	$64.45	$64.45	$64.40
Purchase #6	$158.98	12.529%	$178.8986	$178.90	$178.90	$178.90
Purchase #7	$102.84	8.360%	$111.4374	$111.44	$111.45	$111.40
7 purchase totals =	$936.08		$1,022.5828	$1,022.59	$1,022.60	$1,022.50