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	$107.30	5.413%	$113.1081	$113.11	$113.10	$113.10
Purchase #2	$112.85	4.775%	$118.2386	$118.24	$118.25	$118.20
Purchase #3	$167.85	12.620%	$189.0327	$189.03	$189.05	$189.00
Purchase #4	$167.94	13.195%	$190.0997	$190.10	$190.10	$190.10
Purchase #5	$219.96	10.235%	$242.4729	$242.47	$242.45	$242.50
Purchase #6	$17.43	6.866%	$18.6267	$18.63	$18.65	$18.60
Purchase #7	$167.56	4.131%	$174.4819	$174.48	$174.50	$174.50
7 purchase totals =	$960.89		$1,046.0606	$1,046.06	$1,046.10	$1,046.00