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	$173.78	13.359%	$196.9953	$197.00	$197.00	$197.00
Purchase #2	$97.55	4.351%	$101.7944	$101.79	$101.80	$101.80
Purchase #3	$78.76	4.723%	$82.4798	$82.48	$82.50	$82.50
Purchase #4	$226.75	10.299%	$250.103	$250.10	$250.10	$250.10
Purchase #5	$51.49	13.388%	$58.3835	$58.38	$58.40	$58.40
Purchase #6	$14.43	7.357%	$15.4916	$15.49	$15.50	$15.50
Purchase #7	$70.25	12.195%	$78.817	$78.82	$78.80	$78.80
7 purchase totals =	$713.01		$784.0646	$784.06	$784.10	$784.10