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	$244.73	7.224%	$262.4093	$262.41	$262.40	$262.40
Purchase #2	$82.79	5.595%	$87.4221	$87.42	$87.40	$87.40
Purchase #3	$113.89	5.821%	$120.5195	$120.52	$120.50	$120.50
Purchase #4	$83.33	3.725%	$86.434	$86.43	$86.45	$86.40
Purchase #5	$62.39	5.744%	$65.9737	$65.97	$65.95	$66.00
Purchase #6	$188.88	4.145%	$196.7091	$196.71	$196.70	$196.70
Purchase #7	$39.66	9.529%	$43.4392	$43.44	$43.45	$43.40
7 purchase totals =	$815.67		$862.9069	$862.90	$862.85	$862.80