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	$139.52	8.780%	$151.7699	$151.77	$151.75	$151.80
Purchase #2	$207.54	8.614%	$225.4175	$225.42	$225.40	$225.40
Purchase #3	$102.68	3.682%	$106.4607	$106.46	$106.45	$106.50
Purchase #4	$73.84	6.214%	$78.4284	$78.43	$78.45	$78.40
Purchase #5	$16.35	12.391%	$18.3759	$18.38	$18.40	$18.40
Purchase #6	$104.32	9.168%	$113.8841	$113.88	$113.90	$113.90
Purchase #7	$227.41	12.773%	$256.4571	$256.46	$256.45	$256.50
7 purchase totals =	$871.66		$950.7936	$950.80	$950.80	$950.90