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	$201.29	4.503%	$210.3541	$210.35	$210.35	$210.40
Purchase #2	$173.38	9.448%	$189.7609	$189.76	$189.75	$189.80
Purchase #3	$181.65	3.121%	$187.3193	$187.32	$187.30	$187.30
Purchase #4	$117.35	8.513%	$127.34	$127.34	$127.35	$127.30
Purchase #5	$218.60	9.593%	$239.5703	$239.57	$239.55	$239.60
Purchase #6	$109.75	12.292%	$123.2405	$123.24	$123.25	$123.20
Purchase #7	$113.81	12.394%	$127.9156	$127.92	$127.90	$127.90
7 purchase totals =	$1,115.83		$1,205.5007	$1,205.50	$1,205.45	$1,205.50