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	$148.48	10.685%	$164.3451	$164.35	$164.35	$164.30
Purchase #2	$98.88	12.649%	$111.3873	$111.39	$111.40	$111.40
Purchase #3	$220.88	7.222%	$236.832	$236.83	$236.85	$236.80
Purchase #4	$107.79	7.745%	$116.1383	$116.14	$116.15	$116.10
Purchase #5	$250.28	9.449%	$273.929	$273.93	$273.95	$273.90
Purchase #6	$21.69	13.248%	$24.5635	$24.56	$24.55	$24.60
Purchase #7	$63.42	6.445%	$67.5074	$67.51	$67.50	$67.50
7 purchase totals =	$911.42		$994.7026	$994.71	$994.75	$994.60