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	$181.46	3.530%	$187.8655	$187.87	$187.85	$187.90
Purchase #2	$29.89	4.439%	$31.2168	$31.22	$31.20	$31.20
Purchase #3	$100.75	10.391%	$111.2189	$111.22	$111.20	$111.20
Purchase #4	$221.39	11.513%	$246.8786	$246.88	$246.90	$246.90
Purchase #5	$13.37	7.318%	$14.3484	$14.35	$14.35	$14.30
Purchase #6	$169.26	12.637%	$190.6494	$190.65	$190.65	$190.60
Purchase #7	$250.84	6.246%	$266.5075	$266.51	$266.50	$266.50
7 purchase totals =	$966.96		$1,048.6851	$1,048.70	$1,048.65	$1,048.60