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	$194.29	11.699%	$217.02	$217.02	$217.00	$217.00
Purchase #2	$154.57	6.364%	$164.4068	$164.41	$164.40	$164.40
Purchase #3	$205.43	8.173%	$222.2198	$222.22	$222.20	$222.20
Purchase #4	$33.98	12.586%	$38.2567	$38.26	$38.25	$38.30
Purchase #5	$162.94	3.114%	$168.014	$168.01	$168.00	$168.00
Purchase #6	$102.43	11.825%	$114.5423	$114.54	$114.55	$114.50
Purchase #7	$168.70	12.372%	$189.5716	$189.57	$189.55	$189.60
7 purchase totals =	$1,022.34		$1,114.0312	$1,114.03	$1,113.95	$1,114.00