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	$178.92	9.861%	$196.5633	$196.56	$196.55	$196.60
Purchase #2	$69.94	3.292%	$72.2424	$72.24	$72.25	$72.20
Purchase #3	$174.75	12.166%	$196.0101	$196.01	$196.00	$196.00
Purchase #4	$98.58	13.308%	$111.699	$111.70	$111.70	$111.70
Purchase #5	$161.80	10.264%	$178.4072	$178.41	$178.40	$178.40
Purchase #6	$207.72	4.148%	$216.3362	$216.34	$216.35	$216.30
Purchase #7	$158.95	3.637%	$164.731	$164.73	$164.75	$164.70
7 purchase totals =	$1,050.66		$1,135.9892	$1,135.99	$1,136.00	$1,135.90