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	$165.30	10.859%	$183.2499	$183.25	$183.25	$183.20
Purchase #2	$200.28	9.274%	$218.854	$218.85	$218.85	$218.90
Purchase #3	$165.43	3.870%	$171.8321	$171.83	$171.85	$171.80
Purchase #4	$187.26	5.614%	$197.7728	$197.77	$197.75	$197.80
Purchase #5	$43.82	3.840%	$45.5027	$45.50	$45.50	$45.50
Purchase #6	$65.45	10.515%	$72.3321	$72.33	$72.35	$72.30
Purchase #7	$221.38	9.214%	$241.778	$241.78	$241.80	$241.80
7 purchase totals =	$1,048.92		$1,131.3216	$1,131.31	$1,131.35	$1,131.30