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	$40.36	11.658%	$45.0652	$45.07	$45.05	$45.10
Purchase #2	$216.93	3.863%	$225.31	$225.31	$225.30	$225.30
Purchase #3	$153.71	7.386%	$165.063	$165.06	$165.05	$165.10
Purchase #4	$182.69	5.774%	$193.2385	$193.24	$193.25	$193.20
Purchase #5	$76.60	11.335%	$85.2826	$85.28	$85.30	$85.30
Purchase #6	$112.47	6.330%	$119.5894	$119.59	$119.60	$119.60
Purchase #7	$75.96	6.640%	$81.0037	$81.00	$81.00	$81.00
7 purchase totals =	$858.72		$914.5524	$914.55	$914.55	$914.60