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	$99.61	9.863%	$109.4345	$109.43	$109.45	$109.40
Purchase #2	$37.74	10.589%	$41.7363	$41.74	$41.75	$41.70
Purchase #3	$244.56	13.480%	$277.5267	$277.53	$277.55	$277.50
Purchase #4	$191.45	9.382%	$209.4118	$209.41	$209.40	$209.40
Purchase #5	$107.69	4.493%	$112.5285	$112.53	$112.55	$112.50
Purchase #6	$136.32	3.788%	$141.4838	$141.48	$141.50	$141.50
Purchase #7	$101.44	12.103%	$113.7173	$113.72	$113.70	$113.70
7 purchase totals =	$918.81		$1,005.8389	$1,005.84	$1,005.90	$1,005.70