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	$72.26	8.263%	$78.2308	$78.23	$78.25	$78.20
Purchase #2	$107.95	4.611%	$112.9276	$112.93	$112.95	$112.90
Purchase #3	$36.76	5.874%	$38.9193	$38.92	$38.90	$38.90
Purchase #4	$177.45	4.538%	$185.5027	$185.50	$185.50	$185.50
Purchase #5	$99.29	11.365%	$110.5743	$110.57	$110.55	$110.60
Purchase #6	$243.32	10.362%	$268.5328	$268.53	$268.55	$268.50
Purchase #7	$64.59	11.381%	$71.941	$71.94	$71.95	$71.90
7 purchase totals =	$801.62		$866.6285	$866.62	$866.65	$866.50