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	$130.33	8.478%	$141.3794	$141.38	$141.40	$141.40
Purchase #2	$123.46	8.849%	$134.385	$134.39	$134.40	$134.40
Purchase #3	$161.35	8.213%	$174.6017	$174.60	$174.60	$174.60
Purchase #4	$115.89	9.865%	$127.3225	$127.32	$127.30	$127.30
Purchase #5	$82.41	4.447%	$86.0748	$86.07	$86.05	$86.10
Purchase #6	$217.74	7.771%	$234.6606	$234.66	$234.65	$234.70
Purchase #7	$132.31	9.214%	$144.501	$144.50	$144.50	$144.50
7 purchase totals =	$963.49		$1,042.9250	$1,042.92	$1,042.90	$1,043.00