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	$102.56	4.743%	$107.4244	$107.42	$107.40	$107.40
Purchase #2	$97.26	12.584%	$109.4992	$109.50	$109.50	$109.50
Purchase #3	$52.75	8.334%	$57.1462	$57.15	$57.15	$57.10
Purchase #4	$11.54	8.534%	$12.5248	$12.52	$12.50	$12.50
Purchase #5	$132.82	9.402%	$145.3077	$145.31	$145.30	$145.30
Purchase #6	$242.90	10.814%	$269.1672	$269.17	$269.15	$269.20
Purchase #7	$218.26	3.362%	$225.5979	$225.60	$225.60	$225.60
7 purchase totals =	$858.09		$926.6674	$926.67	$926.60	$926.60