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	$184.45	3.580%	$191.0533	$191.05	$191.05	$191.10
Purchase #2	$84.26	9.270%	$92.0709	$92.07	$92.05	$92.10
Purchase #3	$47.78	11.511%	$53.28	$53.28	$53.30	$53.30
Purchase #4	$74.54	7.764%	$80.3273	$80.33	$80.35	$80.30
Purchase #5	$153.94	9.524%	$168.6012	$168.60	$168.60	$168.60
Purchase #6	$57.68	10.128%	$63.5218	$63.52	$63.50	$63.50
Purchase #7	$190.32	11.179%	$211.5959	$211.60	$211.60	$211.60
7 purchase totals =	$792.97		$860.4504	$860.45	$860.45	$860.50