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	$108.58	10.120%	$119.5683	$119.57	$119.55	$119.60
Purchase #2	$204.92	5.792%	$216.789	$216.79	$216.80	$216.80
Purchase #3	$62.80	10.806%	$69.5862	$69.59	$69.60	$69.60
Purchase #4	$159.48	4.382%	$166.4684	$166.47	$166.45	$166.50
Purchase #5	$109.26	6.226%	$116.0625	$116.06	$116.05	$116.10
Purchase #6	$147.79	3.166%	$152.469	$152.47	$152.45	$152.50
Purchase #7	$157.78	13.378%	$178.8878	$178.89	$178.90	$178.90
7 purchase totals =	$950.61		$1,019.8312	$1,019.84	$1,019.80	$1,020.00