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	$88.95	9.329%	$97.2481	$97.25	$97.25	$97.20
Purchase #2	$199.76	8.181%	$216.1024	$216.10	$216.10	$216.10
Purchase #3	$73.57	7.110%	$78.8008	$78.80	$78.80	$78.80
Purchase #4	$155.78	10.678%	$172.4142	$172.41	$172.40	$172.40
Purchase #5	$70.35	10.675%	$77.8599	$77.86	$77.85	$77.90
Purchase #6	$170.78	9.560%	$187.1066	$187.11	$187.10	$187.10
Purchase #7	$140.96	3.615%	$146.0557	$146.06	$146.05	$146.10
7 purchase totals =	$900.15		$975.5877	$975.59	$975.55	$975.60